The SQL database indicated that the data file has exceeded the maximum size or the hard drive it is located on has run out ...

The SQL database indicated that the data file has exceeded the maximum size or the hard drive it is located on has run out of space.  This prevents further requests from being processed.  The Lync Server service will be shut down.

Cause: The capacity of the hard drive is not sufficient to meet the total load.
Resolution:
Refer to the reference guide for information on fixing this error.