The host uses the designated preferred path, if it has been configured. Otherwise, the host selects the first working path discovered at system boot time. If you want the host to use a particular preferred path, specify it through the

, or by using

esxcli storage nmp psp fixed deviceconfig set

. See Changing Path Policies.

The default policy for active-active storage devices is

VMW_PSP_FIXED

.

The host selects the path that it used most recently. When the path becomes unavailable, the host selects an alternative path. The host does not revert back to the original path when that path becomes available again. There is no preferred path setting with the MRU policy. MRU is the default policy for active-passive storage devices.

The

VMW_PSP_MRU

ranking capability allows you to assign ranks to individual paths. To set ranks to individual paths, use the

esxcli storage nmp psp generic pathconfig set

command. For details, see the VMware knowledge base article 2003468.

The host uses an automatic path selection algorithm that rotates through all active paths when connecting to active-passive arrays, or through all available paths when connecting to active-active arrays. Automatic path selection implements load balancing across the physical paths available to your host. Load balancing is the process of spreading I/O requests across the paths. The goal is to optimize throughput performance such as I/O per second, megabytes per second, or response times.

VMW_PSP_RR

is the default for a number of arrays and can be used with both active-active and active-passive arrays to implement load balancing across paths for different LUNs.