Fibre Channel” (page 39) for procedures on implementing and configuring the
•A path policy of
•A path policy of "fixed" and the preferred/active paths manually set to balance I/O load evenly across all paths is the preferred multipath implementation for ESX 3.0 - 3.5.
◦In the event the active path is detected as having failed or has been disabled either at the fabric switch, or on the storage array, all ESX host I/O to the storage array continues by failing over to a 'standby' path. When the ESX host detects that the preferred path has been recovered or is enabled, I/O from the ESX host then resumes on the preferred path
◦I/O from the ESX host should be manually distributed or balanced when two or more paths exist to more than one HP 3PAR StoreServ Storage volume on the storage array. Manually balancing the loads across available paths may improve I/O performance.
This path load balancing to the storage array is dependant on the number of I/Os that are targeted for specific volumes on the storage array. Tuning I/Os to specific volumes on specific paths to the storage array varies from configuration to configuration and is totally dependant on the workload from the ESX host and the virtual machines to the devices on the storage array.
The following vSphere client screen shot depicts a LUN with five I/O paths in a FIXED I/O policy scheme. The path marked Active (I/O) with the '*' in the Preferred column is the path chosen as preferred, and is the path to which all I/O is currently assigned for the given LUN. The other paths listed are active, but in 'standby' mode. The paths in active 'standby' will not be used for I/O traffic for this LUN unless the preferred path fails.
