Host made an attempt to access a VMFS datastore that is locked by another host.
I/O error, perhaps caused by bad shutdown due to power failure, or faulty controller/connection.
You may attempt to reload the VMFS volume metadata with the following command:
# vmkfstools -B <vmfs device>
Refer to this VMware KB article for more information.
Refer to the VMware Online Documentation for more information on vCenter event messages and possible solutions.