Viewing the multipathing information of a LUN
SAN storage presented to the ESXi hosts should be highly available. This can be achieved by configuring multiple connectivity paths between the ESXi hosts and the SAN storage. Once configured correctly, these paths can then be used to either failover or load balance I/O.
A path to a LUN includes the HBA (Host Bus Adapter)/initiator, the fabric/network switches, and the storage controllers at the array. The availability of a path will be affected if any of these hardware components along the path stop functioning.
Storage multipathing on ESXi hosts is achieved with the help of a framework of APIs called PSA (Pluggable Storage Architecture). These APIs can be used by the storage vendors to write their own Multipathing Plugins (MPP). At the time of writing this book, there were three third-party MPP available:
EMC PowerPath
Dell EqualLogic MEM for iSCSI Multipathing
