Storage array performance is one of the major factors contributing to the performance of the entire SAN environment.

If there are issues with storage array performance, be sure to consult your storage array vendor’s documentation for any relevant information.

When assigning LUNs, remember that each LUN is accessed by a number of ESX/ESXi hosts, and that a number of virtual machines can run on each host. One LUN used by an ESX/ESXi host can service I/O from many different applications running on different operating systems. Because of this diverse workload, the RAID group containing the ESX/ESXi LUNs should not include LUNs used by other hosts that are not running ESX/ESXi for I/O intensive applications.

Make sure read/write caching is enabled.

SAN storage arrays require continual redesign and tuning to ensure that I/O is load balanced across all storage array paths. To meet this requirement, distribute the paths to the LUNs among all the SPs to provide optimal load balancing. Close monitoring indicates when it is necessary to manually rebalance the LUN distribution.

Tuning statically balanced storage arrays is a matter of monitoring the specific performance statistics (such as I/O operations per second, blocks per second, and response time) and distributing the LUN workload to spread the workload across all the SPs.


Dynamic load balancing is not currently supported with ESX/ESXi.