System information

Figure 5-1. How Boot from a SAN Works
storage array
boot disk
host
FC switch
HBA
service
console
VMkernel
NOTE When you use boot from SAN in conjunction with ESX hosts, each host must have its own boot LUN.
Benefits of Boot from SAN
Booting your ESX host from a SAN provides numerous benefits.
The benefits include:
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Cheaper servers – Servers can be more dense and run cooler without internal storage.
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Easier server replacement – You can replace servers and have the new server point to the old boot location.
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Less wasted space.
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Easier backup processes – The system boot images in the SAN can be backed up as part of the overall SAN
backup procedures.
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Improved management – Creating and managing the operating system image is easier and more efficient.
Getting Ready for Boot from SAN
In addition to the general ESX with SAN configuration tasks, complete the following tasks to enable your ESX
host to boot from SAN.
1 Ensure that the configuration settings meet the basic boot from SAN requirements.
2 Prepare the hardware elements.
This includes your HBA, network devices, and storage system. Refer to the product documentation for
each device.
3 Configure LUN masking on your SAN.
This ensures that each ESX host has a dedicated LUN for the boot partitions. The boot LUN must be
dedicated to a single server.
4 Choose the location for the diagnostic partition.
Diagnostic partitions can be put on the same LUN as the boot partition. Core dumps are stored in
diagnostic partitions.
IMPORTANT Your host cannot boot from the EMC CLARiiON CX storage systems that use the ALUA protocol.
With ALUA enabled, these storage systems do not support SCSI-2 reservations, which ESX requires to boot
from a SAN LUN.
Fibre Channel SAN Configuration Guide
44 VMware, Inc.