When you set up your ESXi host to boot from a SAN, your host's boot image is stored on one or more LUNs in the SAN storage system. When the host starts, it boots from the LUN on the SAN rather than from its local disk.

ESXi supports booting through a Fibre Channel host bus adapter (HBA) or a Fibre Channel over Ethernet (FCoE) converged network adapter (CNA).

Boot from SAN Benefits

Boot from SAN can provide numerous benefits to your ESXi environment. However, in certain cases, boot from SAN is not compatible with your hosts. Before you set up your system for boot from SAN, decide whether it is appropriate for your environment.

Caution: When you use boot from SAN with multiple ESXi hosts, each host must have its own boot LUN. If you configure multiple hosts to share the boot LUN, ESXi image corruption might occur.

If you use boot from SAN, the benefits for your environment include the following:

  • Cheaper servers. Servers can be more dense and run cooler without internal storage.
  • Easier server replacement. You can replace servers and have the new server point to the old boot location.
  • Less wasted space. Servers without local disks often take up less space.
  • Easier backup processes. You can back up the system boot images in the SAN as part of the overall SAN backup procedures. Also, you can use advanced array features such as snapshots on the boot image.
  • Improved management. Creating and managing the operating system image is easier and more efficient.
  • Better reliability. You can access the boot disk through multiple paths, which protects the disk from being a single point of failure.

Requirements and Considerations when Booting from Fibre Channel SAN

Your ESXi boot configuration must meet specific requirements.

Table 1. Boot from SAN Requirements
Requirement Description
ESXi system requirements Follow vendor recommendations for the server booting from a SAN.
Adapter requirements Configure the adapter, so it can access the boot LUN. See your vendor documentation.
Access control
  • Each host must have access to its own boot LUN only, not the boot LUNs of other hosts. Use storage system software to make sure that the host accesses only the designated LUNs.
  • Multiple servers can share a diagnostic partition. You can use array-specific LUN masking to achieve this configuration.
Multipathing support Multipathing to a boot LUN on active-passive arrays is not supported because the BIOS does not support multipathing and is unable to activate a standby path.
SAN considerations If the array is not certified for a direct connect topology, the SAN connections must be through a switched topology. If the array is certified for the direct connect topology, the SAN connections can be made directly to the array. Boot from SAN is supported for both switched topology and direct connect topology.
Hardware-specific considerations If you are running an IBM eServer BladeCenter and use boot from SAN, you must deactivate IDE drives on the blades.

Getting Ready to Boot ESXi from SAN

When you prepare your ESXi host to boot from a SAN, you perform several tasks.

This workflow describes the generic boot-from-SAN enablement process on the rack-mounted servers. For information on enabling the boot from SAN option on blade servers or other types of hosts, refer to partner documentation.

For more information, see https://www.vmware.com/resources/compatibility/search.php.

Configure SAN Components and Storage System

Before you set up your ESXi host to boot from a SAN LUN, configure SAN components and a storage system.

Because configuring the SAN components is vendor-specific, refer to the product documentation for each item.

Procedure

  1. Connect network cable, referring to any cabling guide that applies to your setup.
    Check the switch wiring, if there is any.
  2. Configure the storage array.
    1. From the SAN storage array, make the ESXi host visible to the SAN. This process is often called creating an object.
    2. From the SAN storage array, set up the host to have the WWPNs of the host’s adapters as port names or node names.
    3. Create and assign LUNs.
    4. Record the IP addresses of the switches and storage arrays.
    5. Record the WWPN for each SP.
    Caution: If you use a scripted installation process to install ESXi in boot from SAN mode, take special steps to avoid unintended data loss.

Configure Storage Adapter to Boot from SAN

When you set up your host to boot from SAN, you enable the boot adapter in the host BIOS. You then configure the boot adapter to initiate a primitive connection to the target boot LUN.

Prerequisites

Determine the WWPN for the storage adapter.

Procedure

  • ♦ Configure the storage adapter to boot from SAN.
    Because configuring boot adapters is vendor-specific, consult your vendor documentation.

Set Up Your System to Boot from Installation Media

When setting up your host to boot from SAN, you first boot the host from the VMware installation media. To boot from the installation media, change the system boot sequence in the BIOS setup.

Because changing the boot sequence in the BIOS is vendor-specific, refer to vendor documentation for instructions. The following procedure explains how to change the boot sequence on an IBM host.

Procedure

  1. Power on your system and enter the system BIOS Configuration/Setup Utility.
  2. Select Startup Options and press Enter.
  3. Select Startup Sequence Options and press Enter.
  4. Change the First Startup Device to [CD-ROM].

Results

You can now install ESXi.