User Guide SA2500/WA2500 LSI MegaRAID SAS
LSI MegaRAID SAS 8704ELP
RAID Controller Card
SA2500/WA2500
LSIiBBU05 Battery Backup Unit
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Proprietary Notice and Liability Disclaimer
The information disclosed in this document, including all designs and related materials,
is the valuable property of NEC Computers and/or its licensors. NEC Computers and/
or its licensors, as appropriate, reserve all patent, copyright and other proprietary rights
to this document, including all design, manufacturing, reproduction, use, and sales
rights thereto, except to the extent said rights are expressly granted to others.
To allow for design and specification improvements, the information in this document
is subject to change at any time, without notice. Reproduction of this document or
portions thereof without prior written approval of NEC Computers is prohibited.
The NEC Computers product(s) discussed in this document are warranted in
accordance with the terms of the Warranty Statement accompanying each product.
However, actual performance of each product is dependent upon factors such as system
configuration, customer data, and operator control. Since implementation by customers
of each product may vary, the suitability of specific product configurations and
applications must be determined by the customer and is not warranted by NEC
Computers.
Trademarks
NEC ESMPRO, NEC DianaScope, NEC MWA, and ExpressBuilder are trademarks or
registered trademarks of NEC Corporation.
LSI Logic, the LSI Logic logo design, Fusion-MPT, and MegaRAID are trademarks or
registered trademarks of LSI Logic Corporation.
Adobe, and Adobe Acrobat are registered trademarks of Adobe Systems, Incorporated.
Microsoft, Microsoft Windows, Windows NT, Windows 95, Windows 98, Windows
2000 and Windows Server 2003 are all registered trademarks of Microsoft Corporation.
Intel and Xeon are registered trademarks of Intel Corporation.
AMD is a trademark of Advanced Micro Devices, Inc.
All other product, brand, or trade names used in this publication are the trademarks or
registered trademarks of their respective trademark owners.
rev 1.0 May 2007
Copyright 2007
All Rights Reserved
NEC Computers S.A.S.
10 rue Godefroy
Immeuble OPTIMA
92821 PUTEAUX
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Table of Contents
Proprietary Notice and Liability Disclaimer ............................................................... 3
Trademarks .................................................................................................................. 3
Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Text Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Safety Notices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Regulatory Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
European Notice .............................................................................................................. 7
USA and Canada Notice .................................................................................................. 8
Modifications to the Product............................................................................................ 8
CE and FCC Marking ................................................................................................. 8
Connections and Remote Earths ...................................................................................... 8
PELV (Protected Extra Low Voltage) ........................................................................ 8
SELV (Safety Extra Low Voltage) ............................................................................. 8
Remote Earths ............................................................................................................. 8
Building Supply .......................................................................................................... 8
Power Supply and Cables ................................................................................................ 9
Power Supply .............................................................................................................. 9
Cables .......................................................................................................................... 9
Batteries ........................................................................................................................... 9
Chassis Cover Removal and Replacement ...................................................................... 9
Laser Compliance Statement ......................................................................................... 10
Warning - Hazardous Voltage! ...................................................................................... 10
Warning -Avoid Electrostatic Discharge!...................................................................... 10
Product Disposal ............................................................................................................ 10
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
SAS Controller Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
General Description ....................................................................................................... 13
LSISAS1078 Features: .............................................................................................. 13
Supported RAID Levels ............................................................................................ 14
Configuration Scenarios ................................................................................................ 15
Benefits of the SAS Interface ........................................................................................ 16
PCI Express Architecture .......................................................................................... 16
Summary of SAS RAID Controller Characteristics ...................................................... 17
SAS Features ............................................................................................................. 17
SAS Array Limitations .............................................................................................. 18
SATA II Features ...................................................................................................... 18
PCI Express Performance ......................................................................................... 18
Usability Features ..................................................................................................... 19
Flexibility Features ................................................................................................... 19
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Drive Roaming .......................................................................................................... 19
Drive Migration ......................................................................................................... 20
Hardware Specifications ................................................................................................ 21
MegaRAID SAS Hardware Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Quick Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Detailed Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SAS Device Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23
24
25
28
Connecting the SAS RAID Controller with Internal Connectors to Physical Disks ..... 30
After Installing the RAID Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
MegaRAID SAS RAID Controller Characteristics . . . . . . . . . . . . . . . . . . . 32
MegaRAID SAS 8704ELP RAID Controller................................................................ 32
RAID Controller Characteristics ................................................................................... 33
Technical Specifications ................................................................................................ 33
RAID Controller Specifications ................................................................................ 33
Array Performance Features ..................................................................................... 34
Fault Tolerance ......................................................................................................... 35
Electrical Characteristics ........................................................................................... 35
Operating and Non-operating Conditions ................................................................. 36
Safety Characteristics ................................................................................................ 36
Battery Backup Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Installing the Battery Backup Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Installing the LSIiBBU05 .............................................................................................. 38
Connecting to the RAID Controller Using a Board-to-Board Connector
(Daughtercard) .......................................................................................................... 39
Using the Battery Backup Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Monitoring BBUs with the MegaRAID Configuration Utilities ................................... 43
Monitoring BBUs with the WebBIOS Configuration Utility ................................... 43
Monitoring BBUs with MegaCLI.................................................................................. 44
Display BBU Information ......................................................................................... 44
Display BBU Status Information .............................................................................. 44
Display BBU Capacity .............................................................................................. 45
Display BBU Design Parameters .............................................................................. 45
Display Current BBU Properties ............................................................................... 46
Start BBU Learning Cycle ........................................................................................ 46
Place Battery in Low-Power Storage Mode .............................................................. 46
Set BBU Properties ................................................................................................... 46
Monitoring Battery Backup Units with MegaRAID Storage Manager ......................... 47
Replacing Battery Backup Units.................................................................................... 47
Disposing of Battery Backup Units ............................................................................... 48
Battery Backup Unit Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Specifications................................................................................................................. 49
Battery Life and Data Retention Time........................................................................... 49
Glossary of Terms and Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
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Text Conventions
This guide uses the following text conventions.
Warnings, cautions, and notes have the following meanings:
Warning
Warnings alert you to situations that could result in serious personal injury or loss of life.
Caution
Cautions indicate situations that can damage the system hardware or software.
Notes: give important information about the material being
described.
■ Names of keyboard keys are printed as they appear on the keyboard. For example,
Ctrl, Alt, or Enter.
■ Text or keystrokes that you enter appear as boldface type. For example, type
abc123 and press ENTER.
■ File names are printed in upper case letters. For example, AUTOEXEC.BAT.
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Safety Notices
Caution
To reduce the risk of electric shock which could cause personal
injury, follow all the safety notices.
Symbols are shown in your documentation and on your
equipment to indicate safety hazards.
Regulatory Information
European Notice
Products with the CE marking comply with both the Electromagnetic Compatibility
Directive (89/336/EEC) and the Low Voltage Directive (73/23/EEC) - modified by the
Directive 93/68/EEC - issued by the Commission of the European Community.
Compliance with these directives implies conformity to the following European
Standards:
■ EN55022: Radio Frequency Interference
■ EN55024 (1998+A1:2001): Immunity characteristics
■ EN6100-3-2: Limits for harmonic current emissions
■ EN6100-3-3: Limitation of voltage fluctuation and flicker in low-voltage supply
system
■ EN60950-1 (2001): Product Safety
Warning
This is a Class A product. In domestic environment this product
may cause radio interference in which case the user may be
required to take adequate measures (EN55022).
If your system includes a telecommunication network board, the input/output socket is
classified as Telecommunication Network Voltage (TNV-3).
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USA and Canada Notice
Products with UL marking comply with the following UL standards:
■ UL 1950 (3rd edition 1998)
Products with FCC marking comply with the following FCC standards
■ FCC part 15
The model type/ref. used for UL and FCC certification can be found on the regulatory
labels stuck on your system.
The equipment has been tested and found to comply with the limits for a Class A or B
digital device, pursuant to part 15 of the FCC rules. These limits are designed to
provide reasonable protection against harmful interference when the equipment is
operated in a commercial environment. This equipment generates, uses, and can radiate
radio frequency energy, and if not installed and used in accordance with the instruction
manual, may cause harmful interference to radio communications. Operation of this
equipment in a residential area is likely to cause harmful interference, in which case the
user will be required to correct the interference at his own expense.
Modifications to the Product
CE and FCC Marking
We cannot be held responsible for modifications made by the User and the
consequences thereof, which may alter the conformity of the product with the CE or
FCC Marking.
Connections and Remote Earths
PELV (Protected Extra Low Voltage)
To ensure the extra-low voltage integrity of the equipment, only connect equipment
with mains-protected electrically-compatible circuits to the external ports.
SELV (Safety Extra Low Voltage)
Every input and output of this product is classified as Safety Extra Low Voltage.
Remote Earths
To prevent electrical shock, connect all local (individual office) systems and system
support equipment to the same electrical circuit of the building wiring. If you are
unsure, check the building wiring to avoid remote earth conditions.
Building Supply
Only connect the equipment to a building supply that is in accordance with current
wiring regulations in your country. In the U.K., those are the IEE regulations.
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Power Supply and Cables
Power Supply
■ The DC push-button on/off switch on the front panel does not turn off the system
AC power. +5vdc is present on the system board whenever the AC power cords are
connected between the system and an AC outlet. Before doing the procedures in
this manual, make sure that your system is powered off and unplug the AC power
cords from the back of the chassis. Failure to disconnect power before opening
your system can result in personal injury and equipment damage.
■ Under no circumstances should the user attempt to disassemble the power supply.
The power supply has no user-replaceable parts. Inside the power supply are hazardous voltages that can cause serious personal injury. A defective power supply
must be returned to your dealer.
Cables
■ In the U.S.A. and Canada, the power cord must be a UL-listed detachable power
cord (in Canada, CSA-certified), type ST or SJT, 16 AWG, 3-conductor, provided
with a moulded-on NEMA type 5-15 P plug cap at one end and a moulded-on cord
connector body at the other end. The cord length must not exceed 9 feet (2.7
meters).
■ Outside the U.S.A. and Canada, the plug must be rated for 250 VAC, 10 amp
minimum, and must display an international agency approval marking. The cord
must be suitable for use in the end-user country. Consult your dealer or the local
electrical authorities if you are unsure of the type of power cord to use in your
country. The voltage change occurs via a switch in the power supply.
■ The detachable power supply cords are intended to serve as the disconnect devices.
■ For PLUGGABLE EQUIPMENT, the socket-outlet shall be installed near the
equipment and shall be easily accessible.
■ This equipment has a 3-wire, grounded power cords. To prevent electrical hazards,
do not remove or defeat the ground prong on the power cords. Replace a power
cord if it gets damaged. Contact your dealer for an exact replacement.
Batteries
Lithium batteries can be dangerous. Improper handling of lithium batteries may result
in an explosion. Dispose of lithium batteries as required by local ordinance. Also see
“Product Disposal” on page 10
Chassis Cover Removal and Replacement
When servicing your system, make sure to replace the chassis cover and secure it with
the screws before plugging in the power cable and turning it on. The chassis cover
ensures proper airflow and cooling.
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Laser Compliance Statement
The optical devices are tested and certified to be compliant with International Electrotechnical Commission IEC60825-1 and European EN60825-1 standards for Class 1
laser products.
Class 1 laser products are not considered hazardous. The optical devices are designed
such that there is never human access to laser radiation above a Class 1 level during
normal operation or prescribed maintenance conditions.
The optical devices installed in your system are designed for use solely as a component
of such electronic product and therefore do not comply with the appropriate
requirements of Code of Federal Regulation Sec. 1040.10 and Sec. 1040.11 for
COMPLETE laser products
Warning - Hazardous Voltage!
Hazardous voltage is present inside your system when it is connected to an AC supply
even when the system’s power switch is off. Exposure to Hazardous Voltage could
cause personal injury. To reduce the risk of electric shock which could cause personal
injury, follow all safety notices. The symbols shown are used in your documentation
and on your equipment to indicate safety hazards.
Warning -Avoid Electrostatic Discharge!
Circuit cards and integrated circuits can be easily damaged by static electricity. To
reduce risk of damage, store them in protective packaging whenever they are not
installed in your system.
Before you install or remove memory modules, video memory, disk drives, circuit
cards or other devices, protect them from static electricity. To do so, make sure your
system’s power switch is OFF. Then, unplug the system’s AC power cord(s). Wear an
anti-static wrist strap (available at electronic supplies stores) to handle the device you
want to install. Be sure to connect the wrist strap to an unpainted metal portion of the
system chassis.
As an alternative, you can dissipate electrostatic buildup by touching an unpainted
metal portion of the system chassis with one hand. Handle the device you are installing
with the other hand, and maintain continuous contact with the unpainted portion of the
chassis until it is installed in the system.
Product Disposal
The Waste Electrical and Electronic Equipment (WEEE) Directive
requires that used electrical and electronic products must be disposed of
separately from normal household waste in order to promote reuse,
recycling and other forms of recovery and to reduce the quantity of waste
to be eliminated with a view to reducing landfill. WEEE includes
accessories such as keyboard, mouse, remote control, speakers, etc. When you dispose
of such products, please follow the agreement made between you and us and/or your
distributor.
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Overview
This chapter provides a general overview of the MegaRAID SAS 8704ELP controller
with RAID control capabilities.
The MegaRAID SAS RAID controllers are high-performance intelligent PCI Expressto-SCSI/Serial ATA II adapters with RAID control capabilities. MegaRAID SAS RAID
controllers provide reliability, high performance, and fault-tolerant disk subsystem
management. They are an ideal RAID solution for the internal storage of workgroup,
departmental, and enterprise systems. MegaRAID SAS RAID controllers offer a
cost-effective way to implement RAID in a server.
SAS technology brings a wealth of options and flexibility with the use of SAS and
Serial ATA (SATA) II devices within the same storage infrastructure. However, SAS
and SATA devices bring individual characteristics that make each one a more suitable
choice depending on your storage needs. MegaRAID gives you the flexibility to
combine these two similar technologies on the same controller, within the same
enclosure, and in the same virtual disk.
Note: We recommend that you carefully assess any
decision to mix SAS and SATA drives within the same virtual
disk(s). Though it can be done, we strongly discourage the
practice.
The MegaRAID SAS RAID controllers are based on the LSI Logic first-to-market SAS
IC technology and proven MegaRAID technology. As second-generation PCI Express
RAID controllers, the MegaRAID SAS RAID controllers address the growing demand
for increased data throughput and scalability requirements across midrange and
enterprise-class server platforms. LSI Logic offers a family of MegaRAID SAS RAID
controllers addressing the needs for both internal and external solutions.
The LSI Logic intelligent Battery Backup Unit 05 provides cached data protection and
allow system builders to protect cached data even during the most catastrophic system
failures. Refer to the MegaRAID Battery Backup Unit User ’s Guide on the
ExpressBuilder disc for more information about these batteries.
The SAS controllers support the ANSI Serial Attached SCSI standard, version 1.1. In
addition, the controller supports the SATA II protocol defined by the Serial ATA
specification, version 1.0a. Supporting both the SAS and SATA II interfaces, the SAS
controller is a versatile controller that provides the backbone of both server and highend workstation environments.
Each port on the SAS RAID controller supports SAS and/or SATA II devices using the
following:
■ SAS Serial SCSI Protocol (SSP), which enables communication with other SAS
devices.
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■ SATA II, which enables communication with other SATA II devices.
■ Serial Management Protocol (SMP), which communicates topology management
information directly with an attached SAS expander device.
■ Serial Tunneling Protocol (STP), which enables communication with a SATA II
device through an attached expander.
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SAS Controller Description
The MegaRAID SAS 8704ELP PCI Express 1078-based Low-Profile Serial-Attached
SCSI/SATA II Disk Array Controller controls four internal SAS/SATA ports through
one Mini SAS 4i internal connector
General Description
The MegaRAID 1078-based SAS RAID controllers bring 3.0 Gbit/s Serial Attached
SCSI and 3.0 Gbit/s SATA II performance to host adapter, workstation, and server
designs. The controllers support internal and external storage devices, which allows
you to use a system that supports enterprise-class SAS and desktop-class SATA II
drives. Each MegaRAID 1078-based SAS RAID controller can connect to drives
directly and can use expanders to connect to additional drives. Simplified cabling
between devices is an additional benefit.
These SAS controllers are based on the LSISAS1078 RAID On-a-Chip (ROC) device
that is compliant with the Fusion-MPT™ architecture, and provides a PCI Express x4
or x8 interface.
Note: The MegaRAID SAS 8704ELP RAID controller
provides a x4 PCI Express interface.
LSISAS1078 Features:
■ Provides an eight lane, 2.5 Gbit/s PCI Express host-interface, eight 3.0 Gbit/s SAS/
SATA ports, and a full-featured, hardware-based RAID implementation.
■ Integrates a high speed DDR/DDR2 SDRAM interface with a hardware RAID
assist engine for parity calculations.
■ Provides the maximum benefits of a RAID system, and enables you to configure
the system to satisfy your system requirements.
■ Increases system performance and provides fault tolerant data storage.
■ Supports data striping across multiple disks, which reduces disk access time since
multiple disks simultaneously read or write data.
■ Backs up data with either data mirroring or a parity block. Either back up method
enables the user to recover lost data in the event of a disk failure. You can select the
data backup method that best suits your needs. A hardware RAID assist exclusiveOR (XOR) engine speeds parity generation and checking and reduces system
access times.
■ Supports the PCI Express Specification, Revision 1.0a. The PCI Express software
is backward compatible with previous revisions of the PCI bus and PCI-X bus.
■ The SAS RAID controllers integrate eight high-performance SAS/SATA II PHYs
and a PCI Express bus master DMA core. Each of the eight PHYs is capable of 3.0
Gbit/s SAS link rates and 3.0 Gbit/s SATA II link rates.
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■ Supports the SAS protocol as described in the Serial Attached SCSI Standard,
version 1.1.
■ Supports the Serial ATA II (SATA II) protocol defined by the Serial ATA
Specification, Version 1.0a and the Serial ATAII: Extension to the Serial ATA
Specification, Version 1.1. SATA II is an extension to SATA 1.0a. In addition, the
SAS RAID controllers support the following SATA II features:
- 3 Gbit/s SATA II.
- Staggered spin-up.
- Hot Plug.
- Native Command Queuing.
- Activity and fault indicators for each PHY.
- Port Selector (for dual-port drives).
■ Each port on the SAS controllers supports SAS and/or SATA II devices using the
SSP (Serial SCSI Protocol), SMP (Serial Management Protocol), STP (Serial
Tunneling Protocol), and SATA II. The SSP enables communication with other
SAS devices. SATA II enables the SAS controllers to communicate with other
SATA II devices.
Supported RAID Levels
The controller supports disk arrays using the following RAID levels:
■ RAID 0 (data striping): Data is striped across all disks in the array, enabling very
fast data throughput. There is no data redundancy. All data is lost if any disk fails.
■ RAID 1 (disk mirroring): Data is written simultaneously to two disks, providing
complete data redundancy if one disk fails. The maximum array capacity is equal
to the available size of the smaller of the two hard drives.
■ RAID 5 (disk striping with distributed parity): Data is striped across all disks in the
array. Part of the capacity of each disk stores parity information that reconstructs
data if a disk fails. RAID 5 provides good data throughput for applications with
high read request rates.
■ RAID 6 (disk striping with distributed parity across two disks): Data is striped
across all disks in the array and two parity disks are used to provide protection
against the failure of up to two physical disks. In each row of data blocks, two sets
of parity data are stored.
■ RAID 10 (RAID 1 and RAID 0 in spanned arrays): RAID 10 uses mirrored pairs of
disks to provide complete data redundancy. RAID 10 provides high data
throughput rates.
■ RAID 50 (RAID 5 and RAID 0 in spanned arrays): RAID 50 uses both parity and
disk striping across multiple disks to provide complete data redundancy. RAID 50
provides high data throughput rates.
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■ RAID 60 (RAID 6 and RAID 0 in spanned arrays): RAID 60 uses both distributed
parity across two parity disks and disk striping across multiple disks to provide
complete data redundancy. RAID 60 provides high fault tolerance.
Configuration Scenarios
There are three main scenarios in which you can use the SAS RAID controllers:
■ Low-end, internal SATA II configurations: as a high-end SATA II compatible
controller that connects up to four disks either directly or through a port expander.
Enclosure management through out-of-band I2C bus. Mostly for low-end/entry
servers. Side bands of both types of internal SAS connectors support the SFF-8485
(SGPIO) interface.
■ Midrange internal SAS configurations: like internal SATA II configurations, but
with high-end disks. More suitable for low- to mid-range servers.
■ High-end external SAS/SATA II configurations: both internal and external connectivity. Disks can be either SATA II, SAS or a combination of both. External enclosure management through in-band, SCSI-enclosed storage. STP and SMP need to
be supported.
Figure 1 shows a direct-connect configuration. The Inter-IC (I 2 C) interface
communicates with peripherals. The external memory bus provides a 32-bit memory
bus, parity checking, and chip select signals for pipelined synchronous burst static
random access memory (PSBRAM), nonvolatile static random access memory
(NVSRAM), and Flash ROM.
Note: The external memory bus is 32-bit for the SAS
8704ELP.
Figure 1: Example of LSI Logic SAS Direct-Connect Application
SAS/SATA II Device
SAS/SATA II Device
SAS
PCI Express
RAID Controller
SAS/SATA II Device
SAS/SATA II Device
PCI Express Interface
15
32-Bit Memory
Address/Data
Bus
I2 C
Interface
Flash ROM/
PSBRAM/
NVSRAM
I2 C
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Figure 2 shows an example of a SAS RAID Controller configured with an LSISASx12
expander that is connected to SAS and/or SATA II disks.
Figure 2: Example of LSI Logic SAS RAID Controller
Configured with LSISASx12 Expander
PCI Express Interface
8
SAS RAID Controller
LSISAS1078
PCI Express to SAS ROC
SAS/SATA
Drives
LSISASx12
SAS/SATA II
Drives
SAS/SATA II
Drives
Peripheral
Bus
72-bit DDR/DDR2
with ECC
Interface
Flash ROM/
NVSRAM/
I2C/UART
SRAM
SDRAM
SRAM
LSISASx12
SAS/SATA II
Drives
SAS/SATA II
Drives
Benefits of the SAS Interface
SAS is a serial, point-to-point, enterprise-level device interface that leverages the
proven SCSI protocol set. SAS is a convergence of the advantages of SATA II, SCSI,
and fibre channel, and is the future mainstay of the enterprise and high-end workstation
storage markets. SAS offers a higher bandwidth per pin than parallel SCSI, and
improves signal and data integrity.
The SAS interface uses the proven SCSI command set to ensure reliable data transfers,
while providing the connectivity and flexibility of point-to-point serial data transfers.
The serial transmission of SCSI commands eliminates clock skew challenges. The SAS
interface provides improved performance, simplified cabling, smaller connectors,
lower pin count, and lower power requirements when compared to parallel SCSI.
SAS controllers leverage a common electrical and physical connection interface that is
compatible with Serial ATA technology. The SAS and SATA II protocols use a thin,
7-wire connector instead of the 68-wire SCSI cable or 26-wire ATA cable. The SAS/
SATA II connector and cable are easier to manipulate, allow connections to smaller
devices, and do not inhibit airflow. The point-to-point SATA II architecture eliminates
inherent difficulties created by the legacy ATA master-slave architecture, while
maintaining compatibility with existing ATA firmware.
PCI Express Architecture
PCI Express is a local bus system designed to increase data transfers without slowing
down the central processing unit (CPU). You can install MegaRAID PCI Express
RAID controllers in PCI Express computer systems with a standard bracket type. With
these adapters in your system, you can connect SCSI and SATA II devices over the bus.
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PCI Express goes beyond the PCI specification in that it is intended as a unifying I/O
architecture for various systems: desktops, workstations, mobile, server,
communications, and embedded devices.
Summary of SAS RAID Controller Characteristics
This section provides a summary of the features and benefits of the SAS RAID
controller. It contains information on SAS features, SATA II features, PCI
performance, integration, usability, and flexibility.
The MegaRAID SAS RAID controllers include the following features:
■ PCI Express x4 lane width (with support for x8 connections).
■ PCI Express performance up to 2.5 Gbits/s per lane.
■ Support for 128, 256, or 512 Mbyte DDR2 667 MHz on-board SDRAM intelligent
battery backed module.
■ One internal connector for the MegaRAID SAS 8704ELP RAID controller.
■ Support for RAID levels 0, 1, 5, 6, 10, 50, and 60.
■ Advanced array configuration and management utilities.
■ Online RAID level migration.
■ Drive migration.
■ Drive roaming.
■ Patrol read.
■ No reboot necessary after expansion.
■ More than 200 Qtags per array.
■ Hardware clustering support on the board.
■ User-specified rebuild rate.
■ 32 Kbyte nonvolatile random access memory (NVRAM) for storing RAID system
configuration information; the MegaRAID SAS firmware is stored in flash ROM
for easy upgrade.
SAS Features
The following list describes the SAS features of the RAID controllers:
■ Provides eight fully independent PHYs.
■ Supports 3.0 Gbit/s SAS data transfers per PHY.
■ Supports SSP to enable communication with other SAS devices.
■ Supports SMP to communicate topology management information.
■ Provides a serial, point-to-point, enterprise-level storage interface.
■ Simplifies cabling between devices.
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■ Provides a scalable interface that supports up to 122 devices through the use of
expanders (depending on your configuration).
■ Supports wide ports consisting of 2, 3, or 4 PHYs within a single quad port.
■ Supports narrow ports consisting of a single PHY.
■ Transfers data using SCSI information units.
SAS Array Limitations
Table 1: SAS RAID Controller Array Limitations
Maximum
Maximum
Maximum
Virtual
Maximum Virtual
Maximum Maximum Maximum Spans per Maximum
Disks per Arrays per Disks per Drives
Drives per Hot
Virtual
Enclosures Maximum
Controller Controller Array
per Array Controller Spares
Disk
per Port*
Ports
SAS
8704ELP
64
128
16
8
8
16
8
3
1
* - Assumes one SEP (Storage Enclosure Processor) per enclosure.
Note: The maximum number of hot spares per array is
equal to the maximum number of drives per array.
These RAID controllers support 64-bit logical block addressing (LBA), which makes it
possible to connect a large number of drives to the RAID controller, directly and
through expanders. However, the actual number of drives that you can attach depends
on the limits listed in
rather than by actual RAID volume capacity.
SATA II Features
The following list describes the SATA II features of the RAID controllers:
■ Supports SATA II data transfers of 3.0 Gbits/s.
■ Supports STP data transfers of 3.0 Gbits/s.
■ Provides a serial, point-to-point storage interface.
■ Simplifies cabling between devices.
■ Eliminates the master-slave construction used in parallel ATA.
■ Allows addressing of multiple SATA II targets through an expander.
■ Allows multiple initiators to address a single target (in a fail-over configuration)
through an expander.
PCI Express Performance
The following list describes the PCI Express performance features of the RAID
controllers:
■ Provides a PCI Express interface that:
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- Supports a dedicated PCI Express bus.
- Supports x4, x8, or x16 lane configuration.
- Supports transfer rates of up to 2.5 Gbits/s per lane.
- Complies with the PCI Express Specification, Revision 1.0a.
■ Provides unequaled performance through the Fusion-MPT architecture.
■ Provides high throughput and low CPU utilization to offload the host processor.
Usability Features
The following list describes the usability features of the RAID controllers:
■ Simplifies cabling with point-to-point, serial architecture.
■ Supports smaller, thinner cables that do not restrict airflow.
■ Provides drive spin-up sequencing control.
■ Provides up to two LED signals for each PHY to indicate link activity and faults.
■ Provides an I2C interface for enclosure management.
■ Supports the internal SAS Sideband signal SFF-8485 (SGPIO) interface.
Flexibility Features
These features increase the flexibility of the RAID controllers:
■ Supports a Flash ROM interface, a nonvolatile RAM (NVSRAM) interface, and a
pipelined synchronous burst SRAM (PSBRAM) interface.
■ Offers a flexible programming interface to tune I/O performance.
■ Allows mixed connections to SAS or SATA II targets.
■ Leverages compatible connectors for SAS and SATA II connections.
■ Allows grouping of up to four PHYs in a single quad port to form a wide port.
■ Allows programming of the World Wide Name.
Drive Roaming
Drive roaming occurs when the physical disks are changed to different ports on the
same controller. When the drives are placed on different channels, the controller detects
the RAID configuration from the configuration data on the drives.
Note: In a clustering environment, drive roaming is
supported within the same channel only.
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Configuration data is saved in both the NVRAM on the RAID controller and on the
hard drives attached to the controller. This maintains the integrity of the data on each
drive, even if the drives have changed their target ID.
Note: If you move a drive that is being rebuilt, the rebuild
operation will restart, not resume.
Follow these steps to use drive roaming:
1. Turn off all power to the server and all hard drives, enclosures, and system
components, then disconnect power cords from the system.
2. Open the system according to the instructions provided in the system User
Guide.
3. Move the drives to different positions on the backplane to change the targets.
4. Determine the SAS target requirements.
5. Perform a safety check.
a.
Make sure the drives are inserted properly.
b.
Close the cabinet of the host system.
6. Power-on the system.
The controller detects the RAID configuration from the configuration data on
the drives.
Drive Migration
Drive migration is the transfer of a set of hard drives in an existing configuration from
one controller to another. The drives must remain on the same channel and must be
reinstalled in the same order as in the original configuration. The controller to which
you migrate the drives cannot have an existing configuration.
Notes:
■ Only complete configurations can be migrated; individual virtual disks cannot be migrated.
■ Drive roaming and drive migration cannot be supported at
the same time.
Follow these steps to migrate drives:
1. Make sure that you clear the configuration on the system to which you migrate
the drives, to prevent a configuration data mismatch between the hard drives
and the NVRAM.
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Note: When you migrate drives, move only the disks that
make up the virtual disk (not all the physical disks in an array),
so you do not see an NVRAM mismatch error (providing a
configuration is on the destination controller). The NVRAM
mismatch error appears only if you move all of the physical
drives to the other controller.
2. Turn off all power to the server and all hard drives, enclosures, and system
components, then disconnect power cords from the systems.
3. Open the system according to the instructions provided in the system User
Guide.
4. Remove the SAS cable connectors from the internal drives or the shielded
cables from the external drives you want to migrate.
a.
Make sure pin 1 on the cable matches pin 1 on the connector.
b.
Make sure that the SAS cables conform to all SAS specifications.
5. Remove the hard drives from the first system and insert them into drive bays on
the second system.
6. Connect the SAS cables to the hard drives in the second system.
7. Determine the SAS target requirements.
8. Perform a safety check.
a.
Make sure all cables are properly attached.
b.
Make sure the RAID controller is properly installed.
c.
Close the cabinet of the host system.
9. Power-on the system.
The controller detects the RAID configuration from the configuration data on the
drives.
Hardware Specifications
Table 2: MegaRAID SAS RAID controller specifications
Specifications
RAID Levels
Devices Supported per Port
Ports
Data Transfer Rate
Bus
Cache Function
Multiple Virtual Disks/Arrays per Controller
Online Capacity Expansion
Dedicated and Global Hot Spares
Hot Swap Devices Supported
Non-Disk Devices Supported
Mixed Capacity Physical Disks Supported
MegaRAID SAS 8704ELP
0, 1, 5, 6, 10, 50, and 60
Up to 15 SAS or SATA II devices (such as hard drives and
expanders)
Four internal
Up to 3 Gbits/s per phy
PCI Express 1.0a
Write-back, write-through, adaptive read ahead, non-read
ahead, read ahead, cache I/O, direct I/O
Up to 40 virtual disks per controller or per logical array (firmwaredependent)
Yes
Yes
Yes
Yes
Yes
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Table 2: MegaRAID SAS RAID controller specifications (Continued)
Specifications
Number of Internal Connectors
Hardware Exclusive OR (XOR) Assistance
Direct I/O
Architecture
MegaRAID SAS 8704ELP
MegaRAID SAS 8704ELP – One (x4 SAS Port) Mini SAS 4i
connector
Yes
Yes
Fusion-MPT
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MegaRAID SAS
Hardware Installation
This chapter describes the procedures used to install the MegaRAID SAS 8704ELP
controller.
Requirements
The following items are required:
■ A MegaRAID SAS RAID Controller.
■ A host system with an available PCI Express slot.
■ The ExpressBuilder disc, containing the drivers and documentation.
■ The necessary internal and/or external cables.
■ SAS or SATA II physical disks.
Note: We strongly recommend using an uninterruptible
power supply (UPS).
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Quick Installation
The following steps are for quick MegaRAID SAS RAID controller installation. These
steps are for experienced computer users/installers. Refer to “Detailed Installation” on
page 25 if this is not your case.
1. Turn power off to the system, all physical disks, enclosures, and system
components, and remove the PC power cord.
2. Open the cabinet of the host system by following the instructions in the host
system technical documentation.
3. Check the jumper settings and memory module.
4. Install the MegaRAID SAS RAID controller in the server and connect SAS or
SATA II devices to it. Ensure that the cables you use conform to all
specifications.
5. Perform a safety check.
a.
Ensure that all cables are properly attached.
b.
Ensure that the MegaRAID SAS RAID controller is properly installed.
c.
Close the cabinet of the host system.
6. Turn power on after you complete the safety check.
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Detailed Installation
This section provides detailed instructions for installing a MegaRAID SAS RAID
controller.
1. Unpack the RAID Controller.
Unpack and remove the MegaRAID SAS RAID controller. Inspect it for
damage. If it appears damaged, or if any of the following items are missing,
contact your LSI Logic support representative. The MegaRAID SAS RAID
controller is shipped with the following:
- A CD containing MegaRAID drivers for supported operating systems, an
electronic version of this User’s Guide, and other related documentation.
- A license agreement.
- Warranty information.
2. Turn off the Power to the System.
Turn off the computer and remove the AC power cord. Remove the system
cover. Refer to the system documentation for instructions. Before installing the
controller, make sure that the computer is disconnected from the power and
from any networks.
3. Review the MegaRAID Controller Jumpers and Controllers.
The jumpers are set at the factory, and you usually do not need to change them.
Refer to “MegaRAID SAS RAID Controller Characteristics” on page 32 for
diagrams of the MegaRAID SAS RAID controllers with their jumpers and
connectors.
4. Check the Memory Module.
Ensure that the memory module is present and seated firmly in the dual-inline
memory module (DIMM) socket.
Note: The SAS 8704ELP has on-board DDR2 memory.
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5. Install the MegaRAID SAS RAID Controller.
Select a PCI Express slot and align the controller’s PCI Express bus connector
to the slot. Press down gently but firmly to ensure that the card is properly
seated in the slot. Secure the bracket to the computer chassis.
Figure 3: Example of a MegaRAID Board Installation
in a PCI Express Slot
6. Configure and Install the SAS and/or the SATA II Devices in the Host
Computer Case.
Refer to the devices documentation for any preinstallation configuration
requirements.
7. Connect SAS and/or SATA II Devices to the RAID Controller.
Use SAS cables to connect SAS and/or SATA II devices to the MegaRAID
SAS RAID controller. Refer to “SAS Device Cables” on page 28 for SAS
cable information.
8. Turn on the Power to the System.
Replace the computer cover and reconnect the AC power cords. Turn power on
to the host computer. Ensure that the SAS and/or SATA II devices are powered
up before or at the same time as the host computer. If the computer is powered
up before a SAS or SATA II device, the device might not be recognized.
During boot, a BIOS message appears. The firmware takes several seconds to
initialize. The configuration utility prompt times out after several seconds. The
second portion of the BIOS message displays the MegaRAID SAS RAID
controller number, firmware version, and cache SDRAM size. The numbering
of the controllers follows the PCI slot scanning order used by the host
mainboard.
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9. Run the WebBIOS Configuration Utility.
Run the WebBIOS Configuration Utility to configure the physical arrays and
the logical drives. When the message Press CTRL+H for WebBIOS appears
on the screen, press CTRL+H immediately to run the utility.
10. Install the Operating System Driver.
The SAS RAID controllers can operate under various operating systems. To
operate under these operating systems, you must install the software drivers.
The ExpressBuilder disc includes software drivers for the supported operating
systems, along with documentation.
For details on installing the driver, refer to the MegaRAID SAS Device Driver
Installation User’s Guide on the ExpressBuilder disc. Be sure to use the latest
Service Packs provided by the operating system manufacturer and to review
the readme file that accompanies the driver.
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SAS Device Cables
This section describes the cables used on the SAS controllers and provides step-by-step
instructions for connecting SAS and/or SATA II physical disks to the SAS RAID
controller. The SAS and SATA II protocols use a thin, 7-wire connector instead of the
68-wire SCSI cable or 40-wire ATA cable.
Note: Use only straight SAS cables, not cross-over SAS
cables.
Figure 4 displays the SAS cable that connects the internal connectors on a SAS RAID
controller to SAS drives.
Figure 4: Internal SAS Cable for Connection to SAS
and/or SATA II Physical Disks
Hard Drive
Connector
Serial Signal
Cables
RAID Controller to HDD
Breakout Cable
4-Lane Internal
Connector
SFF 8484
Figure 5 displays the SATA II device plug connector used to connect a SAS RAID
controller with internal connectors to the host receptable connector on a backplane. A
SATA II connector consists of a signal connector and a power connector.
Figure 5: SATA II Connectors
Device Plug
Connector
Serial ATA
Signal Connector
(pin 1)
Serial ATA
Power Connector
(pin 1)
Host Receptacle
Connector
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Figure 6 shows SAS and SATA II connectors on SAS and SATA II physical disks,
respectively. Cables are used for connection between internal connectors on the RAID
controllers and connectors on SAS and/or SATA II drives, respectively. Both SAS and/
or SATA II physical disks can connect to SAS backplane receptable connectors. The
difference between the SAS connector and SATA II connector is the bridge between the
SAS primary physical link and power connector on the SAS controller, which the
SATA II connector does not have.
Note: SAS backplane connectors can accept SAS or SATA
II physical disks, but SATA II backplane connectors cannot
accept SAS drives.
Figure 6: SAS and SATA II Plugs
and SAS Backplane Receptacle Connector
SAS Primary
Physical Link
Serial Attached SCSI
Power
SAS Backplane
Receptacle Connector
SAS Secondary
Physical Link
Power
Serial ATA
SAS Secondary
Physical Link
SATA II/SAS
Primary
Physical Link
Power
SATA II
Physical Link
Note: SATA II backplane connectors
do not accept SAS drives.
The following subsections provide step-by-step instructions for connecting the SAS
RAID controllers to SAS and SATA II physical disks, either directly or through an
expander.
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Connecting the SAS RAID Controller with Internal Connectors to
Physical Disks
Follow these steps to connect a SAS RAID controller with internal connectors directly
to SAS and/or SATA II physical disks.
1. Plug the connector on the internal cable into the internal connector on the SAS
RAID controller.
2. Plug the connector on the other end of the internal cable into the connector on
the SAS or SATA II physical disk.
3. If you have another physical disk, connect it to another plug on the internal
cable.
You can connect other devices if the cable has more connectors.
Figure 7: Connecting a SAS RAID Controller
with Internal Connectors to Physical Disks
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After Installing the RAID Controller
After MegaRAID SAS RAID controller installation, you must configure the
MegaRAID SAS RAID controller and install the operating system driver. The
MegaRAID SAS Software User’s Guide instructs you on the configuration options and
how to set them on your MegaRAID SAS RAID controller. The MegaRAID SAS
Device Driver Installation User’s Guide provides detailed installation instructions for
operating system drivers.
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MegaRAID SAS RAID
Controller Characteristics
The MegaRAID 1078-based SAS RAID controllers are dual PHY, SAS PCI Express
RAID controllers and are used in a system with a PCI Express slot. PCI Express goes
beyond the PCI specification in that it is intended as a unifying I/O architecture for
various systems: desktops, workstations, mobile, server, communications, and
embedded devices.
MegaRAID SAS 8704ELP RAID Controller
The MegaRAID SAS 8704ELP PCI Express Low-Profile Disk Array RAID Controller
controls four internal SAS/SATA ports through one (x4 SAS Port) SFF-8087 Mini SAS
4i internal connector.
Figure 8: Card Layout
Table 3: Jumpers and connectors
Jumper Type
Description
J1
2-pin connector.
Cache Write Pending
LEDx
Connector for enclosure LED. Provides a signal that indicates when the onboard cache contains data and a write from the cache to the hard drives is
pending. Optional.
J2
On-board BIOS Enable
2-pin shielded header.
The optional BIOS function is enabled or disabled in software depending on
the status of this jumper.
No jumper: BIOS is enabled (default).
Jumper: BIOS is disabled.
J3
Universal Asynchronous
Receiver/Transmitter
debugging (UART)
4-pin connector.
Reserved for LSI Logic use.
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Table 3: Jumpers and connectors
Jumper Type
Description
J5
16-pin connector.
Individual Fault LED
header for 8 ports
Provides LED interface individually to 8 SAS ports. The LED indicates errors
on particular ports.
J6
IPMI-style SMBus
(System Manage-ment)/
I2C header
3-pin shielded header.
Provides enclosure management support.
J7
Board-to-board connector 20-pin connector.
for battery backup unit
daughtercard
Provides interface to the daughtercard that contains the battery backup unit.
J8
x4 SAS Ports 0-3
The x4 SAS connectors connect the cables from the adapter to SAS or
SATA II physical drives, or to a SAS expander
J10
Default Boot Strap
Controller
2-pin connector.
Loads the defaults in case the boot strap controller (the serial ROM that
controls the memory and processor speeds) becomes corrupt.
RAID Controller Characteristics
Table 4 shows the general characteristics for all MegaRAID 1078-based SAS RAID
controllers.
Table 4: MegaRAID SAS RAID controller Characteristics
Flash ROMa
Serial EEPROMb SAS Data Transfers
SCSI Features
Yes
Yes
Plug and Play Scatter/Gather
Activity LED
a.
b.
Up to 3 Gbits/s per port
SCSI
Termination
Active
For boot code and firmware.
For BIOS configuration storage.
Each MegaRAID 1078-based SAS RAID controller ensures data integrity by
intelligently validating the compatibility of the SAS domain. The MegaRAID 1078based SAS RAID controllers use Fusion-MPT architecture, which allows for thinner
drivers and better performance.
Technical Specifications
The design and implementation of the MegaRAID 1078-based SAS RAID controllers
minimize electromagnetic emissions, susceptibility to radio frequency energy, and the
effects of electrostatic discharge. The MegaRAID SAS RAID controllers carry the CE
mark, C-Tick mark, FCC Self-Certification logo, Canadian Compliance Statement,
Korean MIC, Taiwan BSMI, and Japan VCCI, and they meet the requirements of
CISPR Class B.
The MegaRAID SAS 8704ELP (Model 01116), and LSIiBBU05 (Model 01117) are
CSA C22.2 No. 60950-1, UL 60950-1 First Edition listed Accessory, UL file number
E257743.
RAID Controller Specifications
Table 5 lists the specifications for the MegaRAID 1078-based SAS RAID controllers.
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Table 5: RAID Controller Specifications
Specification
MegaRAID SAS 8704ELP
Processor
SAS 8704ELP RAID Controller: LSISAS1078 with Integrated PowerPC processor
(PCI Express Host
Controller to PCI
Secondary I/O
Controller)
Part Number
SAS 8704ELP RAID Controller: 01116
LSIiBBU05 intelligent Battery Backup Unit 05: 01117
Operating Voltage
+3.3 V, +12 V
Card Size
Low-profile PCI Express adapter card size (6.600" x 2.713")
Array Interface
to Host
PCI Express Rev 1.0a
PCI Express Bus
Data Transfer Rate
Up to 2.5 Gbits/s per lane
Serial Port
3-pin RS232-compatible connector (for manufacturing use only)
SAS Controller(s)
One LSISAS1068 Single SAS controller
SAS Bus Speed
3 Gbits/s
SAS Ports
SAS connectors with four SAS ports each
x4, x8, and x16 lane width
Cache Configuration • 128 MB - 40b arrangement
backed module
• 256 MB - 40b arrangement
backed module
• 256 MB - 72b arrangement
backed module
• 512 MB - 72b arrangement
backed module
Size of Flash ROM
for Firmware
(3) 32Mx16, Double Data Rate II @ 667 MHz battery(3) 64Mx16, Double Data Rate II @ 667 MHz battery(3) 32Mx16, Double Data Rate II @ 667 MHz battery(3) 64Mx16, Double Data Rate II @ 667 MHz battery-
4 Mbytes
Nonvolatile Random 32 Kbytes for storing RAID configurations
Access Memory
(NVRAM)
Array Performance Features
Table 6: Array Performance Features
Specification
MegaRAID SAS 8704ELP
PCI Express Host Data Transfer Rate
2.5 Gbits/s per lane
Drive Data Transfer Rate
3.0 Gbits/s per lane
Maximum Scatter/Gathers
26 elements
Maximum Size of I/O Requests
6.4 Mbytes in 64 Kbyte stripes
Maximum Queue Tags per Drive
As many as the drive can accept
Stripe Sizes
8, 16, 32, 64, or 128 Kbyte
Maximum Number of Concurrent
Commands
255
Support for Multiple Initiators
Yes
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Fault Tolerance
Table 7: Fault Tolerance Features
Specification
MegaRAID SAS 8704ELP
Support for SMARTa
Yes
Optional Battery Backup for Cache
Memory
LSIiBBU05 battery backup. <3.6V/880mAH battery pack;
up to 72 hours of data retention for 128 Mbytes
Drive Failure Detection
Automatic
Drive Rebuild Using Hot Spares
Automatic
Parity Generation and Checking
Yes
a.
The Self Monitoring Analysis and Reporting Technology (SMART) detects up to 70 percent of all
predictable disk drive failures. In addition, SMART monitors the internal performance of all motors,
heads, and drive electronics.
Electrical Characteristics
Power Supply Requirements
All power is supplied to the controller through the PCI Express 3.3V and 12V rails.
Onboard switching regulator circuitry operating from the 12V and the 3.3V rails
provide the necessary voltages. The following states determine the typical current
consumption of the controller:
- State 1: During a hard reset.
- State 2: During a disk stress test.
- State 3: While sitting idle at the DOS prompt.
The supply voltages are 12V +/- 8% (from PCI edge connector only) and 3.3V +/- 9%
(from PCI edge connector only).
Table 8: Power Supply
PCI Edge Connector
State 1
State 2
State 3
3.3V supply
330mA
330mA
330mA
+12V supply
1.00A
1.81A
1.53A
3.3V AUX. supply
30mA
30mA
30mA
Notes: The voltage level used in the charging circuitry for
the battery pack on the optional battery backed daughter board.
If the iBBU DIMM is mounted the following expected power consumption figures apply:
■ During trickle charging of the battery pack: Trickle charge not
available for IBBU
■ During fast charging of the battery pack: 200ma [need verification]
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Operating and Non-operating Conditions
The operating (thermal and atmospheric) conditions are:
- Relative humidity range is 5% to 90% noncondensing (20% to 80% noncondensing for the RAID controllers).
- Airflow must be at least 200 linear feet per minute (LFPM) to avoid operating
the processor above the maximum ambient temperature.
The parameters for the non-operating (such as storage and transit) environment are:
- Temperature range: −30 °C to +80 °C without battery backup unit.
- Temperature range: 0 °C to +45 °C with battery backup unit.
Safety Characteristics
All MegaRAID 1078-based SAS RAID controllers meet or exceed the requirements of
UL flammability rating 94 V0. Each bare board is also marked with the supplier name
or trademark, type, and UL flammability rating. For the boards installed in a PCI
Express bus slot, all voltages are lower than the SELV 42.4 V limit.
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Battery Backup Unit
Introduction
The battery backup unit protects the integrity of the cached data on a MegaRAID RAID
controller by providing backup power if there is a complete AC power failure or a brief
power outage. The LSI Logic MegaRAID iBBU provides an inexpensive alternative to
using an uninterruptible power supply (UPS), and a second level of fault tolerance
when used in conjunction with a UPS.
The cache memory available on MegaRAID controllers can improve overall system
performance. Writing data to the controllers cache memory is much faster than writing
it to a storage device. Write operations appear to complete very quickly at the software
application level. The RAID controller then writes the cached data to the storage device
when system activity is low or when the cache is getting full. The risk of using writeback cache is that the cached data can be lost if the AC power fails before it has been
written to the storage device. This risk factor is eliminated when using an onboard
iBBU.
The MegaRAID iBBUs monitor the voltage level of the DRAM modules installed on
the RAID controller. (Some types of iBBUs are installed directly on the daughtercard
with the DRAM modules.) If the voltage drops below a predefined level, the battery
backup module switches the memory power source from the RAID controller to the
battery pack attached to the iBBU. As long as the voltage level stays below the
predefined value, the iBBU provides power for memory. If the voltage level returns to
an acceptable level, the iBBU switches the power source back to the RAID controller,
and all pending writes to storage devices are completed with no data loss.
An intelligent BBU has built-in functionality to charge the battery pack automatically
and to communicate battery status information such as voltage, temperature, and
current, to the host computer system.
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Installing the Battery Backup Unit
This chapter explains how to install the iBBUs for MegaRAID 1078-based SAS RAID
controllers.
Caution
Electrostatic discharge can damage the iBBUs and the MegaRAID RAID controllers on which they are installed. Always
ground yourself and/or use a ground strap before touching the
RAID controller or the iBBU. Perform all installation work at an
ESD-safe workstation that meets the requirements of EIA625—“Requirements for Handling Electrostatic Discharge Sensitive Devices.” Follow the ESD-recommended practices in the
latest revision of IPC-A-610.
Use an ESD-safe Phillips screwdriver to attach the iBBU to the RAID controller. Set
the screwdriver to a maximum torque of 2.25 inch pounds, and be sure the screwdriver
is centered in the screw to avoid damaging the screw head. If you exceed the maximum
torque specification, you may damage the board, connectors, or screws, and you will
void the warranty of the board.
The batteries in the iBBUs must recharge for at least six hours during fast charge under
normal operating conditions. To protect your data, LSI Logic recommends that you set
the RAID controller Write Policy to write-through until the battery unit is fully
charged. When the battery unit is charged, you can change the Write Policy to writeback to take advantage of the performance improvements of data caching.
The maximum ambient temperature for the battery packs is 45 °C.
Note: The temperature of the battery packs are generally 15–
20 degrees higher than the ambient temperature during fast
charge. Therefore, to complete fast charge cycle, ambient
temperature should be less than 45 °C. If the ambient
temperature exceeds 45 °C, the fast charge cycle will terminate
prematurely, thus preventing the battery pack from reaching a
fully charged state.
Installing the LSIiBBU05
The LSIiBBU05 Intelligent BBU is compatible with systems that offer auxiliary power.
Battery charging and recharging take place automatically. The LSIiBBU05 features
NiMH battery cell technology.
The LSIiBBU05 mounts directly to the SAS RAID controller using a small board-toboard connector (daughtercard).
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Figure 9 displays the top view and the bottom view of the card, the 2-56 screws, and
the 7/32” standoffs. (The “top” side is the side you can see after you install the
LSIiBBU05 on the RAID controller.) Note that this unit combines a battery pack with a
daughtercard.
Figure 9: LSIiBBU05 and Components
1: 5-pin J2 connector
2: J1 connector
3: J14 connector
4: Battery pack harness connector
Connecting to the RAID Controller Using a Board-to-Board Connector
(Daughtercard)
Follow the steps in this section to install the LSIiBBU05 on the SAS controller.
If the RAID controller is already installed in a computer, follow these steps to remove it
before you install the LSIiBBU05:
1. Shut down the computer, turn off the power, and unplug the power cord(s).
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2. Remove the cover from the computer according to the instructions in the
system user’s manual so you can access the RAID controller.
3. Ground yourself before touching the RAID controller.
4. Unplug all cables from the RAID controller, remove the screw attaching the
bracket to the computer case, and carefully remove the RAID controller from
the slot.
5. Place the RAID controller on a flat, clean, static-free surface, and continue
with the next section.
Follow these steps to install the LSIiBBU05. All components are installed on the
bottom of the card. The battery is installed on the top. The maximum height of
components installed on LSIiBBU05 is 0.125”.
1. Ground yourself, and remove the LSIiBBU05 daughtercard from the package.
2. Insert the battery pack harness connector (4) at the end of the colored wires into
the 5-pin J2 connector (1) on the backside of the LSIiBBU05.
3. With the front side up, place the RAID controller on a flat, clean, static-free
surface.
4. Hold the LSIiBBU05 daughtercard so that the battery side is up and the J14
connector (3) lines up with the J7 BBU connector on the RAID controller, as
shown in Figure 10.
Figure 10: Installing the LSIiBBU05 Daughtercard on the
MegaRAID SAS 8708ELP RAID Controller
(The procedure is identical on the MegaRAID SAS 8704ELP controller)
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5. Carefully press the LSIiBBU05 onto the RAID controller, so that the two
connectors are firmly joined.
6. Secure the LSIiBBU05 to the RAID controller with the 2-56 screws and the
standoffs in the three screwholes.
7. The standoffs are threaded at both ends and a 2-56 screw goes into each end.
8. Use the Phillips-head screws that are provided to secure the LSIiBBU05 to the
RAID controller, as shown in Figure 10.
Caution
Center the screwdriver carefully to avoid stripping the screwh ea d . Do n ot o v e r-tighten the scre ws. T he ma xim um
recommended torque is 2.25 inch pounds.
9. Install the RAID controller in the computer in the PCI Express slot, as shown
in Figure 11. Press down gently, but firmly, to ensure that the RAID controller
is properly seated in the slot. The bottom edge of the RAID controller must be
flush with the slot.
Caution
Never apply pressure to the LSIiBBU05 when you insert the
RAID controller. Instead, press down only on the top edge of the
RAID controller, as shown in Figure 11.
Figure 11: Installing the MegaRAID SAS 8708ELP RAID Controller
(The procedure is identical on the MegaRAID SAS 8704ELP controller)
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10. Attach the RAID controller to the computer chassis with the bracket screw.
11. Attach the cables, as needed, to the connectors on the MegaRAID RAID
controller.
12. Replace the computer cover and reattach the power cord(s).
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Using the Battery Backup Units
This chapter explains how to monitor and maintain the MegaRAID BBUs used with the
MegaRAID 1078-based SAS RAID controllers. Most of the MegaRAID BBU
functions, such as battery recharging, occur automatically.
You can monitor the battery status (temperature, voltage, and so on) in these
MegaRAID utility programs:
■ MegaRAID WebBIOS Configuration Utility
■ MegaCLI (command line utility)
■ MegaRAID Storage Manager Configuration Utility
Note: This chapter describes only the BBU-related features
of the MegaRAID utility programs. For complete information on
these utilities, see the MegaRAID SAS Software User’s Guide.
The MegaRAID utilities display a counter showing the number of times the battery
pack on the BBU has been recharged. When you replace a BBU, you should run the
utility program and reset this counter to zero for the new BBU.
Note: LSI Logic recommends that you replace the BBU
once per year or after 500 recharge cycles, whichever comes
first.
Monitoring BBUs with the MegaRAID Configuration Utilities
This section describes how you can use the MegaRAID utilities to monitor the
condition of installed BBUs. You can also use these utilities to reset the recharge cycle
counter to zero when you replace a battery pack.
Monitoring BBUs with the WebBIOS Configuration Utility
The MegaRAID WebBIOS Configuration Utility (CU) configures disk arrays and
logical drives. Because the WebBIOS CU resides in the BIOS, it is independent of the
operating system.
Viewing Battery Backup Unit Information
If your SAS RAID controller has a battery backup unit (BBU), you can view
information about it. To do this, follow these steps:
1. Click Adapter Properties on the main WebBIOS CU screen.
2. Click Next to view the second Adapter Properties screen.
3. Click the word Present in the Battery Backup field at the top left of the screen.
The Battery Module screen appears, as shown in Figure 12.
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Figure 12: Battery Module Screen
Most of the Battery Module properties are view-only and are self-explanatory. In the
lower right panel, there are two properties that can be changed. (LSI Logic
recommends that you leave these properties at their default settings.)
A learning cycle is a battery calibration operation performed by the controller
periodically to determine the condition of the battery. To change the length of the
interval between learning cycles, enter a different number of hours for Learn Delay
Interval and click Go.
Monitoring BBUs with MegaCLI
MegaCLI is a character-based, non-GUI, command line utility that you can use to
configure, monitor, and maintain MegaRAID SAS RAID controllers and the devices
connected to them. MegaCLI runs under Red Hat Linux and Microsoft Windows.
You can use the commands in this section to select the settings for BBU-related options
in MegaCLI.
Display BBU Information
Use the command in Table 9 to display complete information about the BBU for the
selected controller(s).
Table 9: Display BBU Information
Convention
CmdTool -AdpBbuCmd -aN|-a0,1,2|-aALL
Description
Displays complete information about the BBU, such as status, capacity information,
design information, and properties.
Display BBU Status Information
Use the command in Table 10 to display complete information about the status of the
BBU, such as temperature and voltage, for the selected controller(s).
Table 10: Display BBU Status Information
Convention
CmdTool -AdpBbuCmd -GetBbuStatus –aN|-a0,1,2|-aALL
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Table 10: Display BBU Status Information (Continued)
Description
Displays complete information about the BBU status, such as the temperature and
voltage. The information displays in the following formats:
BBU Status for Adapter: xx
Battery Type: XXXXXX(string)
Voltage: xx mV
Current: xx mA
Temperature: xx C°
Firmware Status: xx
Battery state: xx
Gas Gauge Status:
Fully Discharged: Yes/No
Fully Charged: Yes/No
Discharging: Yes/No
Initialized: Yes/No
Remaining Time Alarm: Yes/No
Remaining Capacity Alarm: Yes/No
Discharge Terminated: Yes/No
Over Temperature: Yes/No
Charging Terminated: Yes/No
Over Charged: Yes/No
Additional status information displays differently for iBBU and BBU.
For iBBU:
Relative State of Charge: xx
Charger System State: xx
Charger System Ctrl: xx
Charging Current: xx mA
Absolute State of Charge: xx%
Max Error: xx%
For BBU:
Relative State of Charge: xx
Charger Status: xx
Remaining Capacity: xx mAh
Full Charge Capacity: mAh
isSOHGood: Yes/No
Display BBU Capacity
Use the command in Table 11 to display the BBU capacity for the selected
controller(s).
Table 11: Display BBU Capacity Information
Convention
CmdTool -AdpBbuCmd -GetBbuCapacityInfo –aN|-a0,1,2|-aALL
Description
Displays BBU capacity information. The information displays in the following format:
BBU Capacity Info for Adapter: x
Relative State of Charge: xx%
Absolute State of Charge: xx%
Remaining Capacity: xx mAh
Full Charge Capacity: xx mAh
Run Time to Empty: xxx Min
Average Time to Empty: xxx Min
Average Time to Full: xxx Min
Cycle Count: xx
Max Error: xx%
Display BBU Design Parameters
Use the command in Table 12 to display BBU design parameters for the selected
controller(s).
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Table 12: Display BBU Design Parameters
Convention
CmdTool -AdpBbuCmd -GetBbuDesignInfo –aN|-a0,1,2|-aALL
Description
Displays information about the BBU design parameters. The information displays in
the following formats:
BBU Design Info for Adapter: x
Date of Manufacture: mm/dd, yyyy
Design Capacity: xxx mAh
Design Voltage: mV
Serial Number: 0xhhhh
Pack Stat Configuration: 0xhhhh
Manufacture Name: XXXXXX(String)
Device Name: XXXXXX(String)
Device Chemistry: XXXXXX(String)
Display Current BBU Properties
Use the command in Table 13 to display the current BBU properties for the selected
controller(s).
Table 13: Display Current BBU Properties
Convention
CmdTool -AdpBbuCmd -GetBbuProperties –aN|-a0,1,2|-aALL
Description
Displays current properties of the BBU. The information displays in the following
formats:
BBU Properties for Adapter: x
Auto Learn Period: xxx Sec
Next Learn Time: xxxx Sec
Learn Delay Interval: xx Hours
Auto-Learn Mode: Warn via Event/Disabled/Enabled
Start BBU Learning Cycle
Use the command in Table 14 to start the BBU learning cycle on the selected
controller(s). A learning cycle is a battery calibration operation performed by the
controller periodically (approximately every three months) to determine the condition
of the battery.
Table 14: Start BBU Learning Cycle
Convention
CmdTool -AdpBbuCmd -BbuLearn -aN|-a0,1,2|-aALL
Description
Starts the learning cycle on the BBU. No parameter is needed for this option.
Place Battery in Low-Power Storage Mode
Use the command in Table 15 to place the battery into Low-Power Storage mode on
the selected controller(s). This saves battery power consumption.
Table 15: Place Battery in Low-Power Storage Mode
Convention
CmdTool -AdpBbuCmd -BbuMfgSleep -aN|-a0,1,2|-aALL
Description
Places the battery in Low-Power Storage mode. The battery automatically exits this
state after 5 seconds.
Set BBU Properties
Use the command in Table 16 to set the BBU properties on the selected controller(s)
after reading from the file.
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Table 16: Set BBU Properties
Convention
CmdTool -AdpBbuCmd -SetBbuProperties -f<fileName> -aN|-a0,1,2|-aALL
Description
Sets the BBU properties on the selected controller(s) after reading from the file. The
information displays in the following formats:
autoLearnPeriod = 1800Sec
nextLearnTime = 12345678Sec Seconds past 1/1/2000
learnDelayInterval = 24hours Not greater than 7 days
autoLearnMode = 0 0 – Enabled, 1 - Disabled, 2 – WarnViaEvent.
Monitoring Battery Backup Units with MegaRAID Storage Manager
When MegaRAID Storage Manager software is running, you can see the status of all
BBUs connected to controllers in the server by selecting the Physical tab in the left
panel. If a BBU is operating normally, the icon looks like this:
. If it has failed, a red
dot appears next to the icon.
Figure 13 shows the BBU information that appears in the right panel when you select
the Properties tab.
Figure 13: Battery Backup Unit Information
The BBU properties include the following:
■ The number of times the BBU has been recharged (Cycle Count)
■ The full capacity of the BBU, plus the percentage of its current state of charge, and
the estimated time until it will be depleted
■ The current BBU temperature, voltage, current, and remaining capacity
■ If the battery is charging, the estimated time until it is fully charged
Replacing Battery Backup Units
We recommend you replace BBUs once a year or after 500 recharging cycles,
whichever comes first.
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After you install a new BBU, use one of the MegaRAID configuration utilities to reset
the battery recharge cycle counter to zero.
Disposing of Battery Backup Units
Warning
Do not damage the battery pack in any way. Toxic chemicals
can be released if it is damaged.
The material in the battery pack contains heavy metals that can contaminate the
environment. Federal, state, and local regulations prohibit the disposal of rechargeable
batteries in public landfills. Be sure to recycle the old battery packs properly. LSI Logic
reminds you that you must comply with all applicable battery disposal and hazardous
material handling laws and regulations in the country or other jurisdiction where you
are using the BBU.
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Battery Backup Unit Specifications
This chapter includes technical information and specifications for the LSIiBBU05. A
second section lists information about battery life and data retention time.
Specifications
Table 17: Specifications for the LSIiBBU05
LSIiBBU05
Battery Technology
NiMH
Battery Operating Temperature (Ambient) 10–45 °C
Humidity (Storage and Operating)
20% to 80% non-condensing
Battery Storage Temperature
Depends on storage time, as follows:
< 30 days: 0–50 °C 30–90 days: 0–40 °C
> 90 days: 0–30 °C
Battery Voltage Conditioning
<3.6 V
Fast Charge Rate
350 mAH
Battery Pack
4 cells
Mechanical
3.7” x 2.2”
Battery Capacity
880 mAH
Charge Circuitry Card
Yes
Memory Technology
DDR2 SDRAM (1.8 V)
Battery Charge Time
~6 hours
Socket Type
Not applicable
Module Support
DDR2
Cache Memory Size Supported
128 - 256 Mbytes
Memory Bus Speed
667 MHz
Memory Bus Width
Maximum 72-bit
Error Correcting Capability (ECC)
Not applicable
Auxiliary Power
Yesa
a. These battery products have the ability to detect the presence of an external auxiliary power
source. Circuitry on this product automatically chooses auxiliary power to maintain cache contents, deferring battery discharge until auxiliary power is removed or exhausted. Presence of
an auxiliary power source thus increases the overall DRT ratings in Table 18.
Battery Life and Data Retention Time
The MegaRAID utilities display a counter showing the number of times a BBU has
been recharged. When you replace a BBU, you should run the utility program and reset
this counter to zero for the new BBU.
We recommend you replace the battery pack on the BBU once a year or after 500
recharging cycles, whichever comes first.
The data retention times shown in Table 18 are approximate. They can vary based on a
number of factors, including the following:
■ Capacity of the battery pack and the battery load
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■ Ambient temperature
■ Age of the battery and number of discharge cycles it has been through
■ Number of DIMMs installed and number of chips on the installed DIMMs
■ DRAM size
Table 18: Reference Data Retention Times
BBU Name
Data Retention Times
LSIiBBU05
-
72
72
72
72
hours
hours
hours
hours
for
for
for
for
512
256
256
128
Mbytes,
Mbytes,
Mbytes,
Mbytes,
using
using
using
using
five 64 Mx16 parts DDR2 (low power)
five 32 Mx16 parts DDR2 (low power)
three 64 Mx16 parts DDR2 (low power)
three 32 Mx16 DDR2 (low power)
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Glossary of Terms
and Abbreviations
Active Termination
The electrical connection required at each end of the SCSI bus, composed of active
voltage regulation and a set of termination resistors.
Array
An array of disk drives combines the storage space on the disk drives into a single
segment of storage space. A hot spare drive does not actively participate in an array.
BIOS
Acronym for Basic Input/Output System. Software that provides basic read/write
capability. Usually kept as firmware (ROM-based). The system BIOS on the
mainboard of a computer boots and controls the system. The BIOS on your host
adapter acts as an extension of the system BIOS.
Configuration
Refers to the way a computer is set up, the combined hardware components (computer,
monitor, keyboard, and peripheral devices) that make up a computer system, or the
software settings that allow the hardware components to communicate with each other.
Device Driver
A program that allows a microprocessor (through the operating system) to direct the
operation of a peripheral device.
Domain Validation
Domain Validation is a software procedure in which a host queries a device to
determine its ability to communicate at the negotiated data rate.
EEPROM
Acronym for Electronically Erasable Programmable Read-Only Memory. It is a
memory chip that typically stores configuration information, as it provides stable
storage for long periods without electricity and can be reprogrammed. Refer to
NVRAM.
External SAS Device
A SAS device installed outside the computer cabinet. These devices are connected
using specific types of shielded cables.
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Fusion-MPT Architecture
Fusion-MPT (Message Passing Technology) architecture consists of several main
elements: Fusion-MPT firmware, the Fibre Channel and SCSI hardware, and the
operating system level drivers that support these architectures. Fusion-MPT
architecture offers a single binary, operating system driver that supports both Fibre
Channel and SCSI devices.
Host
The computer system in which a RAID controller is installed. It uses the RAID
controller to transfer information to and from devices attached to the SCSI bus.
Host Adapter Board
A circuit board or integrated circuit that provides a device connection to the computer
system.
Hot Spare
An idle, powered on, standby drive ready for immediate use in case of disk failure. It
does not contain any user data. A hot spare can be dedicated to a single redundant array
or it can be part of the global hot-spare pool for all arrays managed by the controller.
When a disk fails, the controller firmware automatically replaces and rebuilds the data
from the failed drive to the hot spare. Data can be rebuilt only from virtual disks with
redundancy (RAID levels 1, 5, 10, and 50; not RAID level 0), and the hot spare must
have sufficient capacity.
Internal SAS Device
A SAS device installed inside the computer cabinet. These devices are connected by
using a shielded cable.
Main Memory
The part of a computer’s memory which is directly accessible by the CPU (usually
synonymous with RAM).
NVRAM
Acronym for Nonvolatile Random Access Memory. An EEPROM (Electronically
Erasable Read-Only Memory chip) that stores configuration information. Refer to
EEPROM.
PCI
Acronym for Peripheral Component Interconnect. A high-performance, local bus
specification that allows the connection of devices directly to computer memory. The
PCI Local Bus allows transparent upgrades from 32-bit data path at 33 MHz to 64-bit
data path at 33 MHz, and from 32-bit data path at 66 MHz to 64-bit data path at 66
MHz.
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PCI Express
Acronym for Peripheral Component Interconnect Express. A high-performance, local
bus specification that allows the connection of devices directly to computer memory.
PCI Express is a two-way, serial connection that transfers data on two pairs of point-topoint data lines. PCI Express goes beyond the PCI specification in that it is intended as
a unifying I/O architecture for various systems: desktops, workstations, mobile, server,
communications, and embedded devices.
Peripheral Devices
A piece of hardware (such as a video monitor, disk drive, printer, or CD-ROM) used
with a computer and under the control of the computer. SCSI peripherals are controlled
through a SAS MegaRAID SAS RAID controller (host adapter).
PHY
The interface required to transmit and receive data packets transferred across the serial
bus.
Each PHY can form one side of the physical link in a connection with a PHY on a
different SATA device. The physical link contains four wires that form two differential
signal pairs. One differential pair transmits signals, while the other differential pair
receives signals. Both differential pairs operate simultaneously and allow concurrent
data transmission in both the receive and the transmit directions.
RAID
Acronym for Redundant Array of Independent Disks (originally Redundant Array of
Inexpensive Disks). An array of multiple independent physical disks managed together
to yield higher reliability and/or performance exceeding that of a single physical disk.
The RAID array appears to the controller as a single storage unit. I/O is expedited
because several disks can be accessed simultaneously. Redundant RAID levels (RAID
levels 1, 5, 10, and 50) provide data protection.
RAID Levels
A set of techniques applied to disk groups to deliver higher data availability, and/or
performance characteristics to host environments. Each virtual disk must have a RAID
level assigned to it.
SAS
Acronym for Serial Attached SCSI. A serial, point-to-point, enterprise-level device
interface that leverages the proven SCSI protocol set. The SAS interface provides
improved performance, simplified cabling, smaller connections, lower pin count, and
lower power requirements when compared to parallel SCSI. SAS controllers leverage a
common electrical and physical connection interface that is compatible with Serial
ATA. The SAS controllers support the ANSI Serial Attached SCSI standard, version
1.0. In addition, the controller supports the Serial ATA II (SATA II) protocol defined by
the Serial ATA specification, version 1.0a. Supporting both the SAS and SATA II
interfaces, the SAS controller is a versatile controller that provides the backbone of
both server and high-end workstation environments. Each port on the SAS RAID
controller supports SAS and/or SATA II devices.
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SAS Device
Any device that conforms to the SAS standard and is attached to the SAS bus by a SAS
cable. This includes SAS RAID controllers (host adapters) and SAS peripherals.
SATA
Acronym for Serial Advanced Technology Attachment. A physical storage interface
standard, SATA is a serial link that provides point-to-point connections between
devices. The thinner serial cables allow for better airflow within the system and permit
smaller chassis designs.
SMP
Acronym for Serial Management Protocol. SMP enables communicates topology
management information directly with an attached SAS expander device. Each PHY on
the controller can function as an SMP initiator.
SSP
Acronym for Serial SCSI Protocol. SSP enables communication with other SAS
devices. Each PHY on the SAS controller can function as an SSP initiator or SSP
target.
STP
Acronym for Serial Tunneling Protocol. STP enables communication with a SATA II
device through an attached expander. Each PHY on the SAS controller can function as
an STP initiator.
Stripe Size
The total disk space consumed by a stripe not including a parity disk. For example,
consider a stripe that contains 64 Kbytes of disk space and has 16 Kbytes of data
residing on each disk in the stripe. In this case, the stripe size is 64 Kbytes and the
stripe element size is 16 Kbytes. The stripe depth is four (four physical disks in the
stripe). You can specify stripe sizes of 8 Kbytes, 16 Kbytes, 32 Kbytes, 64 Kbytes, or
128 Kbytes for each virtual disk. A larger stripe size produces improved read
performance, especially if most of the reads are sequential. For mostly random reads,
select a smaller stripe size.
Striping
Disk striping writes data across two or more disks. Each stripe spans two or more disks
but consumes only a portion of each disk. Each disk, therefore, may have several
stripes. The amount of space consumed by a stripe is the same on each disk included in
the stripe. The portion of a stripe that resides on a single disk is a stripe element.
Striping by itself does not provide data redundancy; striping in combination with parity
provides data redundancy.
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