Multipathing and PSA troubleshooting

PSA is a collection of storage APIs used by a vSphere host using a VMkernel layer. PSA has different components, and its open and modular framework design allows an independent storage design for third-party SAN developers to directly interact with the storage I/O path of vSphere hosts.

PSA manages different plugins that perform different I/O operations, for example, synchronizing the concurrent I/O access, path selection, and load balancing can be defined by multiple multipathing plugins (MPPs), which can be provided by a SAN provider. The two most famous third-party MPPs are as follows:

• Symantec Dynamic Multi-Pathing (http://goo.gl/dTH2PV)

• EMC PowerPath (http://goo.gl/SNJRXr)

The following screenshot presents PSA and depicts how third-party MPPs are plugged into it:

The multipath plugin can publish instructions to the vSphere storage I/O path directly. PSA not only loads and unloads these plugins within VMkernel, it also performs physical path scanning...