ESXi iSCSI SAN Recommendations and Restrictions

To work properly with iSCSI SAN, your ESXi environment must follow specific recommendations. In addition, several restrictions exist when you use ESXi with iSCSI SAN.

For additional information about using vSphere with iSCSI, see Best Practices For Running VMware vSphere On iSCSI blog.

iSCSI Storage Recommendations

• Verify that your ESXi host supports the iSCSI SAN storage hardware and firmware. For an up-to-date list, see VMware Compatibility Guide.
• To ensure that the host recognizes LUNs at startup time, configure all iSCSI storage targets so that your host can access them and use them. Configure your host so that it can discover all available iSCSI targets.
• Unless you are using diskless servers, set up a diagnostic partition on local storage. If you have diskless servers that boot from iSCSI SAN, see General Recommendations for Boot from iSCSI SAN for information about diagnostic partitions with iSCSI.
• Set the SCSI controller driver in the guest operating system to a large enough queue.
• VMtools increases the default disk timeout SCSI TimeoutValue parameter to 180 seconds. On virtual machines without VMtools, increase the value of the SCSI TimeoutValue parameter. With this parameter set up, the VMs can better tolerate delayed I/O resulting from a path failover. For information, see Set Timeout on Windows Guest OS or the KB 1009465.
• Configure your environment to have only one VMFS datastore for each LUN.

iSCSI Storage Restrictions

• ESXi does not support iSCSI-connected tape devices.
• You cannot use virtual-machine multipathing software to perform I/O load balancing to a single physical LUN.
• ESXi does not support multipathing when you combine independent hardware adapters with either software or dependent hardware adapters.