HP 3PAR VMware ESX Implementation Guide

The VI/vSphere client GUI allows for settings to be changed only on a volume-by-volume
(LUN-by-LUN) basis. The GUI is appropriate and preferred for use in managing I/O paths within
theFIXED path policy scheme. See “Configuring Round Robin Multipathing on ESX 4.x or later
for Fibre Channel” (page 41) for procedures on implementing and configuring the round-robin
path policy on ESX/ESXi 4.0 and later with an HP 3PAR StoreServ Storage.
• A path policy of "round-robin" is the preferred multipath implementation for ESX/ESXi 4.0
and later. For procedures on implementing and configuring the round-robin path policy on
ESX/ESXi 4.0 and later with an HP 3PAR StoreServ Storage, see “Configuring Round Robin
Multipathing on ESX 4.x or later for Fibre Channel” (page 41).
• 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 fails or is 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 is recovered or is enabled, I/O from
the ESX host resumes on the preferred path -- as long as a preferred path policy path was
set.
◦ 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 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.
Figure 18 (page 41) shows a LUN with five I/O paths in a FIXED I/O policy scheme. The path
marked Active (I/O) * is the preferred path, and is the path to which all I/O is currently assigned
for the given LUN. The other paths are listed as active, but are in standby mode. The paths in
active standby mode will not be used for I/O traffic for this LUN unless the preferred path fails.
40 Configuring the Host for a Fibre Channel Connection