esx.problem.vmfs.extent.offline
Summary
Host has lost connection to a storage device that backs a VMFS datastore or a datastore extent.
Causes
This event is logged when an host loses connection to storage.
Resolutions
Either a storage device that backs an entire datastore is offline, or one of the extents is offline. Virtual machines that use that storage may become unresponsive or fail.
Locate the device that has failed and restore connectivity. Check cabling and switch connections. Refer to this VMware KB article for further details.
External
Refer to the VMware Online Documentation, especially the vSphere Troubleshooting Guide, for more information on vCenter event messages and possible solutions.