You must meet several requirements for your ESX/ESXi host to work properly with a SAN.

Verify that your SAN storage hardware and firmware combinations are supported in conjunction with ESX/ESXi systems. For an up-to-date list, see the Storage/SAN section of the online Hardware Compatibility Guide.

Configure your system to have only one VMFS datastore for each LUN. In VMFS-3, you do not need to set accessibility.

Unless you are using diskless servers (booting from a SAN), do not set up the diagnostic partition on a SAN LUN. In the case of diskless servers that boot from a SAN, a shared diagnostic partition is appropriate.

Use RDMs for access to any raw disk.

Set the SCSI controller driver in the guest operating system to a large enough queue. You can set the queue depth for the physical HBA during system setup.

On virtual machines running Microsoft Windows, increase the value of the SCSI TimeoutValue parameter to allow Windows to better tolerate delayed I/O resulting from path failover.