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Enabling iSCSI boot under
UEFI boot mode on
Dell 13
th
generation of
PowerEdge servers
A technical white paper detailing the configuration options and process for iSCSI boot for Dell 13 th generation of PowerEdge servers.
Version 2.0
March, 2016
Xi Li, Software Dev Staff Engineer
Paul Rubin, Lifecycle Controller Product Manager
Dell | Enterprise Solutions Group
Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
Contents
Figures
THIS WHITE PAPER IS FOR INFORMATIONAL PURPOSES ONLY, AND MAY CONTAIN TYPOGRAPHICAL ERRORS AND TECHNICAL INACCURACIES.
THE CONTENT IS PROVIDED AS IS, WITHOUT EXPRESS OR IMPLIED WARRANTIES OF ANY KIND.
Copyright © 2016 Dell Inc. All rights reserved. Dell and the Dell logo are trademarks of Dell Inc. in the United States and/or other jurisdictions. All other marks and names mentioned herein may be trademarks of their respective companies
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March 2016 | Version 2.0 ii
Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
Executive summary
With the growing use of network-based server deployment processes, compute grids and softwaredefined services on modern servers require multiple options to enable server network boot. Dell 13 th generation of PowerEdge servers has recently introduced UEFI-based Internet Small Computer System
Interface (iSCSI) boot capabilities that support a range of server deployment and startup scenarios.
This document describes the following aspects for iSCSI boot support configuration within a 13 th generation of PowerEdge server BIOS:
Server network booting; understanding PXE boot and iSCSI boot
Network boot under legacy BIOS and UEFI modes
Configuration of the iSCSI boot feature
The iSCSI boot work flow
Current known limitations of the iSCSI boot feature
Note: iSCSI solutions rely on multiple datacenter infrastructure components such as network switches, storage subsystems, and server operating systems. For information about other iSCSI solution components, see the appropriate documentation.
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Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
Introduction
Network boot is the process of booting a system with an operating image available in a network service. By using network boot, you can reduce the overall data center storage needs, enhance solution reliability through multiple remote boot services, and reduce the recovery time for storage failures.
In the past, Dell PowerEdge servers provided a network boot feature that used the legacy boot mode of individual network interface controllers. This resulted in complexities and performance challenges.
Dell's 13 th generation of PowerEdge servers provide an enhanced network boot support by utilizing the
UEFI boot environment to implement both PXE and iSCSI-based network boot.
Network Boot - PXE and iSCSI
The following are the two commonly used network boot methodologies in the industry:
PXE boot - Uses a program download mechanism through a network interface to download and execute a program without using the local disk storage space.
iSCSI boot - Uses a mechanism called Disk Emulation. Instead of downloading an executable program through a network interface, iSCSI clients or initiators send SCSI commands to a SCSI storage device or target on a remote server and treat the remote storage device as a locally attached storage. iSCSI interactions are used to load an executable program such as an operating system to the memory of the server.
To provide device-independent support for network interfaces from multiple vendors, 13 th generation of PowerEdge server BIOS has recently added an iSCSI boot feature in UEFI boot mode.
iSCSI boot from NIC firmware and iSCSI boot from BIOS
Prior to the availability of the PowerEdge UEFI iSCSI boot feature, the iSCSI boot feature was device and vendor specific. The feature was based on the invocation of an iSCSI boot stack that is provided by the PCI option ROM of the network interface.
This form of iSCSI boot is supported on the legacy BIOS mode of the server and it depends on the various network interfaces to implement the iSCSI boot option ROM code.
Figure 1 illustrates the configuration of a device specific iSCSI boot function.
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Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
Figure 1. Configuring option-ROM based legacy mode iSCSI boot
The 13 th generation of PowerEdge servers UEFI iSCSI boot feature enables efficient multi-vendor support of iSCSI boot by implementing the iSCSI boot function within the PowerEdge UEFI BIOS and by removing the dependency on vendor-specific option ROM support.
The UEFI iSCSI boot feature can be configured through the 13 th generation of PowerEdge BIOS user interface or through the PowerEdge iDRAC with Lifecycle Controller command line interface. This white paper illustrates the UEFI iSCSI boot feature using the BIOS user interface.
Assuming a 13 th generation of PowerEdge BIOS configured for UEFI boot mode, a Network Settings menu (Figure 2) is provided from the System BIOS page user interface, enabling the configuration of
PXE and iSCSI boot using BIOS-based drivers.
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Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
Figure 2. Accessing Network Settings option from PowerEdge UEFI BIOS
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Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
Configuring iSCSI boot parameters
To configure the iSCSI boot parameters, perform the following steps:
1. On the Network Settings page, enter the initiator name in the iSCSI Initiator Name field.
Note: The iSCSI initiator name must follow IQN format, which includes the “iqn.” string, date in yyyymm format, a period (“.”), the reversed domain name of the naming authority, and an optional string within the character set and length boundaries prefixed with a colon (“:”).
2. Select Enabled from the iSCSI Device1 options.
Figure 3. Accessing iSCSI Device1 Settings from Network Settings
3. Click the iSCSI Device1 Settings link.
4. Enable one of the two connections – Connection 1 Settings or Connection 2 Settings as required. For this example, click the Connection 1 Settings link.
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Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
Figure 4. Accessing Connection 1 Settings option from iSCSI Device1 Settings
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Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
Figure 5. iSCSI boot configuration page one
5. Select the network interface to be configured to perform iSCSI boot from the Interface dropdown menu
6. Choose the IPv4 or IPv6 IP protocol as appropriate, and if required, use VLAN, VLAN ID and
VLAN Priority to configure VLAN.
7. Enter appropriate values in the Retry Count and Timeout fields respectively to manage interface error and timeout conditions.
8. Select Enabled or Disabled from the DHCP option.
Note: The DHCP option is used to select manual or DHCP server-based configuration of the initiator
IP, subnet, and gateway addresses. If DHCP is enabled, it is not required to configure the three initiator parameters. If DHCP is disabled, you must manually enter the three initiator parameters.
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Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
Figure 6. iSCSI boot configuration page two
Similarly, the iSCSI target can be configured through a DHCP server or manually. If the DHCP option in the previous step is disabled, the Target info via DHCP automatically selects Disabled.
9. Enter appropriate values in the Target Name, Target Name IP Address, Target Port, and
Target Boot LUN fields respectively for static configuration. If Target info via DHCP is set to
Enabled, the information is obtained from the DHCP sever through DHCP option 17, the root path option.
Target Port is the TCP port that iSCSI uses for communication. The Target Port is set to 3260 by default. Target Boot Lun is the LUN number from which the iSCSI initiator boots.
If required, use the ISID option to set the initiator session identifier. This option is required if more than one iSCSI initiator system is communicating with the same target.
10. Select CHAP to use CHAP for encryption or None from the Authentication Type option.
11. If the authentication type is CHAP, select One Way or Mutual from the CHAP Type option.
12. If CHAP is one way, specify CHAP Name and CHAP Secret. If CHAP is mutual, you must specify Reverse CHAP Name and Reverse CHAP Secret as well.
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Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
iSCSI Boot Workflow
The following flow chart describes the iSCSI boot work flow. After the iSCSI Device1 is enabled and either of the connections is configured according to the above procedure, BIOS iSCSI boot operates as follows:
1. BIOS verifies if the iSCSI initiator name is present and that the format of the initiator name is accurate. If the initiator name is present and accurate, proceed. Otherwise, iSCSI boot exits and displays the following error message:
Unable to perform iSCSI boot because the iSCSI initiator name is invalid .
2. Provide parameters for Interface, Protocol, VLAN, VLAN ID, VLAN Priority, Retry Count, and
Timeout.
3. Check if the DHCP option is enabled. If the option is disabled, proceed to the next step. If the option is enabled, BIOS tries to obtain initiator configuration information from the DHCPv4 or
DHCPv6 server depending on the Protocol parameter obtained in the previous step. BIOS then performs the following additional steps:
Verifies if the connection of DHCP server to the initiator system is present. If the connection is present, proceed; otherwise, BIOS exits and displays the following error message:
Unable to perform iSCSI boot on connection 1/2 because the network connection to DHCPv4 (DHCPv6) server is not established .
Determine if Target info via DHCP option is enabled. If the option is disabled, proceed to the next step. If the option is enabled, BIOS tries to obtain target configuration information from the DHCP server. The target information obtained from the DHCP server is then verified. If the information is accurate, proceed; otherwise, it exits and displays the following error message:
Unable to perform iSCSI boot on connection 1/2 because the iSCSI target configuration data obtained from DHCPv4 (DHCPv6) server is invalid .
Attempts to obtain initiator information from the DHCP server. If the attempt is successful, proceed; otherwise, it exits and displays the following error message:
Unable to perform iSCSI boot on connection 1/2 because the BIOS cannot obtain the initiator information from DHCPv4 (DHCPv6) server.
4. Verify whether the network cable of the server system is present. If the network cable is present, proceed; otherwise, it exits and displays the following error message:
Unable to perform iSCSI boot on connection 1/2 because the network cable is not connected.
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Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
5. Check whether CHAP is enabled. If CHAP is disabled, proceed; otherwise, check whether
CHAP Type is One Way or Mutual. For one way CHAP, obtain CHAP Name and CHAP Secret and then proceed; for mutual CHAP, obtain Reverse CHAP name and Reverse CHAP secret as well, then proceed to the next step.
6. Create a TCP connection to the iSCSI target. If a TCP connection is established within the defined retry count, proceed; otherwise, it exits and displays the following error message:
Unable to perform iSCSI boot on connection 1/2 because the TCP connection timed out when connecting to the iSCSI target .
7. Perform iSCSI login to the target system. If login is successful, proceed with iSCSI boot; If login is unsuccessful, it exits and displays the following error message:
Unable to perform iSCSI boot on connection 1/2 because the iSCSI login operation did not complete successfully .
8. Perform iSCSI boot. Load the executable image to the memory of the server and when the operation is complete, start the image.
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Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
Start
Is initiator name set in correct format?
Yes
Get configuration data:
Network Interface, Protocol,
VLAN info, Retry Count and
Timeout
Is initiator IP/mask/gateway configured by
DHCP?
Yes
No
A
No
Get CHAP name and secret
Yes
No
Is system cable present?
Yes
Is CHAP enabled?
No
Create TCP connection
No
No
Exceed the maximum retry count?
Yes
Is TCP connection established?
Yes
Try iSCSI log in
No iSCSI log in succeed?
Yes
Perform iSCSI boot
B
Figure 7. iSCSI boot work flowchart (1)
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Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
A
Get initiator information from
DHCPv4/DHCPv6 server
No
Is DHCP server system cable present?
Yes
Is target IP/mask/ configured by DHCP?
Yes
Is target information from
DHCP server correct?
Yes
Is initiator information from
DHCP server correct?
No
No
No
Figure 8.
Exit A
B iSCSI boot work flowchart (2)
B
Figure 9.
End iSCSI boot work flowchart (3)
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Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
Current Limitations
At present, the PowerEdge iSCSI software initiator does not support redirection to a new IP address by the iSCSI target while using IPv6.
Under some circumstances such as during load-balancing, the iSCSI target will attempt to redirect an initiator to another target system using a new IP address. In such cases, PowerEdge iSCSI initiators using IPv6 will fail to reestablish a TCP connection and the iSCSI boot will fail.
Conclusion
The new iSCSI boot feature of the 13 th generation of PowerEdge server BIOS enables device and vendor independent iSCSI boot by removing the limitations of vendor-provided option ROM iSCSI boot stacks. With the growing importance of network boot to support server deployment, configuration, and the bootstrap of operating environments for compute grids and software-defined services, the 13 th generation of PowerEdge server iSCSI boot increases the choice of network interfaces while simplifying IT operations.
Dell continues to provide our customers with products that simplify and streamline their IT processes, reduce time and effort of the administrator to focus on activities that help to improve the organization.
For more information on PowerEdge servers and IT automation, see Dell TechCenter .
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Enabling iSCSI boot under UEFI boot mode on Dell 13 th generation of PowerEdge servers
Appendix - Acronyms and Terminology
BIOS: Basic Input / Output System. The BIOS contains programs that are stored on a flash memory chip. The BIOS initializes the systems and loads the operating system.
Legacy BIOS: The de facto 16-bit interface between the OS and the platform firmware. It is based on the original PC BIOS.
UEFI: Unified Extensible Firmware Interface. An industry standard specification that defines a software interface between an operating system and platform firmware. UEFI is replacing Legacy BIOS as the software interface to the OS.
LOM: LAN on Motherboard. Network interfaces that are integrated directly into a motherboard of the system, as opposed to a plug-in NIC.
NDC: Network Daughter Card. Network interfaces that exist on a daughter card as opposed to being integrated directly into the motherboard or added through a plug-in NIC. Many PowerEdge systems use an NDC instead of integrating the LAN support into the motherboard (see LOM).
NIC: Network Interface Card. Typically a plug-in PCIe network adapter, but may also refer to NDC or
LOM’s.
PXE: Preboot eXecution Environment. A specification that allows booting from the network by identifying and then downloading the correct boot image for a system.
iSCSI: A protocol to carry SCSI disk commands over TCP/IP.
IQN format: iSCSI Qualified Name, which contains the
“iqn.”
string, a date code in
yyyy-mm
format, a period (“.”), the reversed domain name of the naming authority, and an optional string within the character set and length boundaries prefixed with a colon (“:”).
VLAN: Virtual Local Area Network. A technology that uses IEEE 802.1Q tagging to identify packets on a single physical connection as belonging to separate virtual networks.
LUN: Logical Unit Number. A target system can contain multiple Logical Units, and address of each
Logical Unit within a target is called a LUN.
TCP: Transmission Control Protocol. A highly reliable host-to-host protocol.
DHCP: Dynamic Host Configuration Protocol. It provides configuration parameters to an internet host.
CHAP: Challenge-Handshake Authentication Protocol. It is used to periodically verify the identity of the peer using a 3-way handshake.
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