go down because of storage failure or administrative error, is properly handled in ESX 5.1 as a
result of feature enhancement performed by VMware. Previously, in ESX versions 5.0 or 4.1, the
host would try continuously to revive the storage links and, as a result, performance would be
impacted for working VMs. A host reboot was required to clear this error.
I was engaged by several customers impacted with APD issue and it was always disaster. If you operate ESX 5.0 and older consider upgrade to ESX 5.1 or even better to ESX 5.5.