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 ESXi host starts, it boots from the LUN on the SAN rather than from its local disk.

You can use boot from the SAN if you do not want to handle maintenance of local storage or have diskless hardware configurations, such as blade systems.

ESXi supports different methods of booting from the iSCSI SAN.

Table 1. Boot from iSCSI SAN support
Independent Hardware iSCSI Software iSCSI
Configure the iSCSI HBA to boot from the SAN. For information on configuring the HBA, see Configure Independent Hardware iSCSI Adapter for SAN Boot. Use the software iSCSI adapter and a network adapter that supports the iSCSI Boot Firmware Table (iBFT) format. For information, see VMware ESXi Installation and Setup.

General Recommendations for Boot from iSCSI SAN

If you plan to set up and use an iSCSI LUN as the boot device for your host, follow certain general guidelines.

The following guidelines apply to booting from the independent hardware iSCSI and iBFT.
  • Review any vendor recommendations for the hardware you use in your boot configuration.
  • For installation prerequisites and requirements, review vSphere Installation and Setup.
  • Use static IP addresses to reduce the chances of DHCP conflicts.
  • Use different LUNs for VMFS datastores and boot partitions.
  • Configure proper ACLs on your storage system.
    • The boot LUN must be visible only to the host that uses the LUN. No other host on the SAN is permitted to see that boot LUN.
    • If a LUN is used for a VMFS datastore, multiple hosts can share the LUN.
  • Configure a diagnostic partition.
    • With the independent hardware iSCSI only, you can place the diagnostic partition on the boot LUN. If you configure the diagnostic partition in the boot LUN, this LUN cannot be shared across multiple hosts. If a separate LUN is used for the diagnostic partition, multiple hosts can share the LUN.
    • If you boot from SAN using iBFT, you cannot set up a diagnostic partition on a SAN LUN. To collect your host's diagnostic information, use the vSphere ESXi Dump Collector on a remote server. For information about the ESXi Dump Collector, see vCenter Server Installation and Setup and vSphere Networking.

Prepare the iSCSI SAN

Before you configure your host to boot from an iSCSI LUN, prepare and configure your storage area network.

Caution: If you use scripted installation to install ESXi when booting from a SAN, you must take special steps to avoid unintended data loss.


  1. Connect network cables, referring to any cabling guide that applies to your setup.
  2. Ensure IP connectivity between your storage system and server.
    Verify configuration of any routers or switches on your storage network. Storage systems must be able to ping the iSCSI adapters in your hosts.
  3. Configure the storage system.
    1. Create a volume (or LUN) on the storage system for your host to boot from.
    2. Configure the storage system so that your host has access to the assigned LUN.
      This step might involve updating ACLs with the IP addresses, iSCSI names, and the CHAP authentication parameter you use on your host. On some storage systems, in addition to providing access information for the ESXi host, you must also explicitly associate the assigned LUN with the host.
    3. Ensure that the LUN is presented to the host correctly.
    4. Ensure that no other system has access to the configured LUN.
    5. Record the iSCSI name and IP addresses of the targets assigned to the host.
      You must have this information to configure your iSCSI adapters.

Configure Independent Hardware iSCSI Adapter for SAN Boot

If your ESXi host uses an independent hardware iSCSI adapter, such as QLogic HBA, you can configure the adapter to boot from the SAN.

This procedure discusses how to enable the QLogic iSCSI HBA to boot from the SAN. For more information and more up-to-date details about QLogic adapter configuration settings, see the QLogic website.


  1. Start the installation media and reboot the host.
  2. Use the BIOS to set the host to boot from the installation media first.
  3. During server POST, press Crtl+q to enter the QLogic iSCSI HBA configuration menu.
  4. Select the I/O port to configure.
    By default, the Adapter Boot mode is set to Disable.
  5. Configure the HBA.
    1. From the Fast!UTIL Options menu, select Configuration Settings > Host Adapter Settings.
    2. (Optional) Configure the following settings for your host adapter: initiator IP address, subnet mask, gateway, initiator iSCSI name, and CHAP.
  6. Configure iSCSI settings.
  7. Save your changes and restart the system.

Configure iSCSI Boot Settings

Configure iSCSI boot parameters, so that your ESXi host can boot from an iSCSI LUN.


  1. From the Fast!UTIL Options menu, select Configuration Settings > iSCSI Boot Settings.
  2. Before you can set SendTargets, set Adapter Boot mode to Manual.
  3. Select Primary Boot Device Settings.
    1. Enter the discovery Target IP and Target Port.
    2. Configure the Boot LUN and iSCSI Name parameters.
      • If only one iSCSI target and one LUN are available at the target address, leave Boot LUN and iSCSI Name blank.

        After your host reaches the target storage system, these text boxes are populated with appropriate information.

      • If more than one iSCSI target and LUN are available, supply values for Boot LUN and iSCSI Name.
    3. Save changes.
  4. From the iSCSI Boot Settings menu, select the primary boot device.
    An auto rescan of the HBA finds new target LUNs.
  5. Select the iSCSI target.
    If more than one LUN exists within the target, you can select a specific LUN ID by pressing Enter after you locate the iSCSI device.
  6. Return to the Primary Boot Device Setting menu. After the rescan, Boot LUN and iSCSI Name are populated. Change the value of Boot LUN to the appropriate LUN ID.