Products which belong to Essentials and Small Business Server family might crash if virtualized on Windows Server 2012 Hyper-V host in the event that the host crashes or loses power. The active directory instance may become corrupted and might result in blue screen/bug check with error:
c00002e2 Directory Services could not start because of the following error: %hs Error Status: 0x%x. Please shutdown this system and reboot into Directory Services Restore Mode, check the event log for more detailed information.
This issue occurs because the Hyper-V virtual IDE controller erroneously reports success if an operating system on the guest requests to disable the disk cache. This might result in an application issuing I/O operations that it believes are persisted to disk that are actually being allowed to reside in the disk cache, which would not be persisted across power failures of the Hyper-V host.
Update Rollup KB2855336 should be installed on Windows Server 2012 Hyper-V host.