After installing Microsoft November update 2014 rollup KB 3000853 http://support.microsoft.com/kb/3000853 MS SQL backup is not performed with Status Not Started and an error  “Data source MS SQL (VSS) is not ready for backup: No VSS writers were found for MS SQL” 
 

If there is a reported error  SQL VSS writer is not in the list of writers (if command vssadmin list writers is executed ).  Performing the restart of SQLServer,  VSS Writer service results in correct state of the writer but it will fail again on the next backup.

Following errors will be tracked in Event log:

EventId 12366 - VSS - An unhandled exception was encountered while processing a VSS writer event callback method. The VSS writer infrastructure is in an unstable state. Restart the service or application that hosts the writer.

 Writer name:            SqlServerWriter

 Writer id:              {a65faa63-5ea8-4ebc-9dbd-a0c4db26912a}

 Writer instance:        {035a4544-2f3f-49a7-8760-0752e40aaa26}

 Process command line:   "C:\Program Files\Microsoft SQL Server\90\Shared\sqlwriter.exe"

 Process ID:             1428

 Writer operation:       1014

 Writer state:           1

 Exception code:         0xe06d7363

 Exception location:     02

EventId 12301 - VSS - Volume Shadow Copy Service error: Writer SqlServerWriter did not respond to a GatherWriterStatus call.

Operation:

   Gather writers' status

   Executing Asynchronous Operation

Context:

   Current State: GatherWriterStatus