Host Managed
Shingled Magnetic
Recording
Mitch Rose
Director Technical Customer Management
Seagate Technology
Contents:
SMR types
Zone Block Devices
Open Source Reference
Host Aware SMR Measured Data
SMR role in HDD offerings
2
Drivers of Data Growth
INTERNET OF THINGS
MOBILITY
Smartphones and Tablets
Nest, Apple Watch, Fitbit,
Google Glass, Wearable
Technology
SURVEILLANCE AND SECURITY
Smart City, Shopping Malls
BIG DATA ANALYTICS
Waze, Splunk, Hadoop
HD AND MEDIA-RICH VIDEO
IPhone 4K Video, Virtual gaming
BIG DATA TO REACH $125B IN 2015
3•
Source: IDC, December 2014
3
Data Explosion vs. Areal Density Growth
SMR
Data Growth
IT Budget shortfall
2011
4Company estimates
2012
Areal Density Growth
2013
2014
2015
2015
2016
2017
4
Storage Trends Driving SMR
• High capacity
– Fast sequential write and read requirements
– Lower random performance – command rate, latency
– SMR disk, tape
• High performance
– Fast random write requirements
– Disk (conventional, high spin speed), Flash, NV storage-class
memories
5
SMR Applications
Application
Capacity Optimized (Cost per capacity priority)
1. Zone Aware storage stack
2. Predominately sequential writing

3.

Host Aware SMR
Fill-once applications
Tolerant of higher command latency variance
Drive Managed SMR
Specifically due to random writes
Performance Optimized (Cost per IOPs priority)
1. Customer doesn’t own stack
2. Cannot tolerate lower performance,
specifically higher command latency
variance
6•
Best Fit
*stack: may include hardware, software, & storage architecture defining key elements of an Application’s QoS (Quality of Service)
Conventional Drives (CMR)
6
Conventional versus SMR Writing
Reader
Writer
Conventional Writing
TrackNN
Track
Track
TrackN+1
N+1
Track
TrackN+2
N+2
Track
TrackN+3
N+3
Writer
Reader
Shingled Writing: 5-track band
TrackNN
Track
TrackN+1
N+1
Track
TrackN+2
N+2
Track
TrackN+3
N+3
Track
TrackN+4
N+4
Track
7
Copyright © Seagate Technology, Dec 2014
SMR - Improving Write Performance
Write-around for
sequential writes
Band 0
Data from host
Band 1
Disk
Cache
• Write-back disk* cache
• Multiple commands cleaned
during a band update
Band 2
…
Band max
* HDD conventional area for caching data.
8
Copyright © Seagate Technology, Dec 2014
ZBC/ZAC Standards
SMR Drive Types
SMR
Category
Description
Drive
Managed
(DM)
Supported Zone Types
Device
Type
Conv.
Seq’l Wr
Required
Seq’l Wr
Preferred
• Backward Compatible
• Drive autonomously hides all SMR issues
• Performance profile changes
00h
n/a
n/a
n/a
Host
Managed
(HM)
• Not backward compatible
• New Device Type
• Error conditions for some reads & writes
• Zoned block device commands
14h
Optional
Required
Not
Allowed
Host
Aware
(HA)
• Backward Compatible
• Superset of Drive Managed and Host
Managed
• Zoned block device command support
00h
Optional
Not
Allowed
Required
9ZBC: Zoned Block Commands (T10 for SAS); ZAC: Zoned-block ATA Commands (T13 for SATA)
© Seagate Technology 2015
9
Advantages of Host Aware
•
Host Aware advantages
Host Aware
– Every Host Aware drive uses underlying
Drive Managed architecture
– Fault tolerant accepting writes not at the
write pointer
– Random write capable inside advisory
limits
Drive Managed
features
Host Managed
features
- A superset of features -
Host Aware Extensions
•
Drive Managed SMR
(foundation)
•
10
Seagate Technology 2015
Host Aware is interchangeable with Host
Managed
– Host Aware uses the same standard as
Host Managed
– If a Host makes the needed changes, HM
and HA will offer competitive performance
10
SMR Bands and Zones
• Conceptually, a zone is one or more bands
Bands
Zones
Groups of tracks
Groups of LBAs
Bx-1
LBA max
•
– Not visible to the host
WP
Zone n-1
Bx-2
…
…
B2
Zone 2
B1
Zone 1
B0
Zone 0
Band: a physical grouping of tracks
•
Zone: a range of LBAs
– Zone configuration is exposed through new
REPORT ZONES command
– Write Pointer and Conventional Zone Types
WP
WP
•
Zone use & Write Pointers (WP)
– Each non-conventional zone has a write pointer
– Write pointers track location for next sequential
write
LBA 0
physical
•
11
• Writes that start at the write pointer advance
the write pointer
logical
ZBC: Zoned Block Commands (T10 for SAS); ZAC: Zoned-block ATA Commands (T13 for SATA)
11
Host Aware Goals
• Enable SMR at parity performance
- Advisory parameters express intended use model
- Minimal use of media cache
- Minimal effect to command latency variance
• In a nutshell
Empty
Zone
Reset
Open
• LBA grouped in zones exposing SMR bands
• Sequential writes go straight to main store
•
•
Reset Write Pointer before re-write
Writes at write pointer do not require read-modify-write
Full
• Random writes go to media cache
• Conventional zones for host metadata
• Lamarr HA: 16 GiB out of 8 TB
•
•
12
Seagate Technology 2015
0.2% of capacity
12
Host Aware SMR Performance
– A micro-benchmark with
workloads that conforms to the
zoned block device intended use
model
– Demonstrates that Host Aware
SMR has parity performance as
CMR when used as intended
– Seagate has modified Iometer to
perform zone-aware workloads
2000
1000
0
250
• Available from Seagate Technical
Support
Seagate Technology 2015
200
150
100
50
0
QD 1 to 128
Transfer Size
•
13
CMR 7200rpm 6TB
HA SMR 5900rpm 8TB
CMR 5900rpm 4TB
3000
WCE Sequential Write MB/s
• Zoned Iometer
4000
WCE Random Write IOPS
• Meet or beat conventional drive
performance
4k
8k
16k
32k
64k
Seagate Confidential
128k
256k
512k
13
1MiB
SATA Host Aware In Linux
User
Space
Software
libzbc / ZAC
libzbc – Adds support for ZAC commands in user space providing the option of
sg_utils
Operation System
Kernel
Space
EXT4 SMR Friendly File System
• Currently working on single drive HDD readiness (v0.5)
• http://www.github.com/seagate/SMR_FS-EXT4
File System / ZAC
Device mapper / LVM
Block Layer (IO scheduler)
SAS
SAT
SCSI
SATA
pass
through
Software RAID – Device mapper solutions being investigated by HDD
vendors for compatibility with legacy non-ZAC compliant file systems
SCSI – SCSI / sd_zbc for ZBC commands
SCSI
SAS HBA/RAID
Expander
application level management
SAT
SAT – Linux patches backward to 2.6
ZAC
libata
libata – ZAC command support (starting 3.18 kernel)
AHCI
SATA HA SMR
14
14
HA SMR – Seagate view of Timeline
Q3 ’15
Seagate HA
SMR Drives
ZBC / ZAC
Standards
File System
EXT4 SMRFFS
15
Q4 ’15
Design in partners engaged
Q1 ’16
HDD qualification
readiness
ZAC projected T13
approved
ZBC T10 approved
V.0.5
FS Changes
Volume production
V.0.6
User Utils
HDD + SMRFFS
integration
V.0.7 projected
milestone
LVM
RAID development
15
Who else is making “friendly” changes for SMR?
Open Source
• Linux File Systems: EXT4, XFS, btrfs, & more
• Software Defined Storage & Object SW
Closed Source / Proprietary
• Efforts underway for FS, Software defined
storage, Hardware partners, & cloud providers
• Nothing to announce, today
16
16
Resources
t10.org
ZBC: SCSI Zoned Block Commands letter
ballot review, now
t13.org
ZAC: ATA Zoned ATA Commands
github.com/hgst/libzbc
Linux user space libraries for application
access to zone block devices
github.com/Seagate/SMR_FS-EXT4
Improvements to ext4 for zoned block
devices
github.com/westerndigitalcorporation/smr-simulator
Device mapper target that emulates a zoned
block device
17
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