To work properly with a SAN, your ESXi host must meet several requirements.
Verify that your ESXi systems support the SAN storage hardware and firmware. For an up-to-date list, see VMware Compatibility Guide.
Configure your system to have only one VMFS datastore for each LUN.
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.
Use RDMs for access to any raw disk. For information, see Raw Device Mapping.
Set the SCSI controller driver in the guest operating system to a large enough queue. For information on changing queue depth for iSCSI adapters and virtual machines, see vSphere Troubleshooting.
On virtual machines running Microsoft Windows, increase the value of the SCSI TimeoutValue parameter. With this parameter set up, the Windows VMs can better tolerate delayed I/O resulting from a path failover. For information, see Set Timeout on Windows Guest OS.