I saw warning in the event log:
Successfully restored access to volume 4fd62ae0-607335c6-3a49-e840f2aca3dc (datastore1) following connectivity
Lost access to volume 4fd62ae0-607335c6-3a49-e840f2aca3dc (datastore1) due to connectivity issues. Recovery
attempt is in progress and outcome will be reported shortly.
Bootbank cannot be found at path '/bootbank' (2013-04-27T03:03:05.040Z cpu0:156952)
Anybody know what it means? It's critical or not?
Mostly it comes from incompatibility problem but your case is a Permanent Device Loss condition.
It's critical if you have production VMs on that datastore, however it still need to be fixed or have a workaround to prevent further problems.