Ah Exchange 2013 server and snapshots. Let me tell you a story. I know someone who did snapshot and exchange server, as a precaution, prior to changing the Outlook Aanywhere settings. The change caused an issue, so he rolled back the snapshot… and the grief was still there.
Exchange 2013 writes a bunch of stuff into AD and of course the snapshot did not revert those changes. A late night was spent by many people to understand and revert the changes in AD
You need to understand what is on a server and how the application(s) behave before snapshotting it.
You need to understand your change process
If you want your application or O/S consistent snapshot, then funnily enough the O/S or application needs to understand you are doing it!
Really good blog here