We have a 3 CAS array. A 2 mailbox server DAG. for the pas 3 days we have been getting events 1177, 1564 & 1135. The CLuster Service is shutting down every night between midnight and 3a.m. There is nothing running that we are aware of and there are no network outages. Trying to figure out what's going on. Can backups against the passive mailbox server effect the DAG. Ais problem?nyone seen th

Are backups running at the time?  And how are you backing these up?

Sounds like you're going to need to generate and then read through the cluster logs.

Hi,

Basis on the event id, it seems related to DAG network or FSW server. Please refer to below link about those ID:
Event ID 1177: https://technet.microsoft.com/en-us/library/cc773498(v=ws.10).aspx
Event ID 1564: https://technet.microsoft.com/en-us/library/cc756221(v=ws.10).aspx
Event ID 1135: https://technet.microsoft.com/en-us/library/cc773460(v=ws.10).aspx

Besides, please generate Cluster.log for further troubleshooting. Heres an blog about How to Troubleshoot Create Cluster failures:
http://blogs.msdn.com/b/clustering/archive/2012/05/07/10301709.aspx

Thanks