Specific considerations apply when you manage storage multipathing plug-ins and claim rules.

The following considerations help you with multipathing:

If no SATP is assigned to the device by the claim rules, the default SATP for iSCSI or FC devices is VMW_SATP_DEFAULT_AA. The default PSP is VMW_PSP_FIXED.

When the system searches the SATP rules to locate a SATP for a given device, it searches the driver rules first. If there is no match, the vendor/model rules are searched, and finally the transport rules are searched. If no match occurs, NMP selects a default SATP for the device.

If VMW_SATP_ALUA is assigned to a specific storage device, but the device is not ALUA-aware, no claim rule match occurs for this device. The device is claimed by the default SATP based on the device's transport type.

The default PSP for all devices claimed by VMW_SATP_ALUA is VMW_PSP_MRU. The VMW_PSP_MRU selects an active/optimized path as reported by the VMW_SATP_ALUA, or an active/unoptimized path if there is no active/optimized path. This path is used until a better path is available (MRU). For example, if the VMW_PSP_MRU is currently using an active/unoptimized path and an active/optimized path becomes available, the VMW_PSP_MRU will switch the current path to the active/optimized one.

If you enable VMW_PSP_FIXED with VMW_SATP_ALUA, the host initially makes an arbitrary selection of the preferred path, regardless of whether the ALUA state is reported as optimized or unoptimized. As a result, VMware does not recommend to enable VMW_PSP_FIXED when VMW_SATP_ALUA is used for an ALUA-compliant storage array.

The exception is when you assign the preferred path to be to one of the redundant storage processor (SP) nodes within an active-active storage array. The ALUA state is irrelevant.

By default, the PSA claim rule 101 masks Dell array pseudo devices. Do not delete this rule, unless you want to unmask these devices.