We've had an interesting VSS-related problem when attempting to take
TimeFinder/Snap backups of a SQL Server database concurrently with a TSM
file system backup. However I suspect this could potentially affect anyone
using a combination of hardware and software providers in VSS.

In our scenario we had a clustered SQL Server instance with user databases
on a LUN from an EMC Symmetrix (P:). We were also using VSS as the
snapshot provider on the TSM file system backups of the local disk (C:).

The problem we encountered was that the periodic snaps that we took of the
databases on P: using Replication Manager would fail whenever there was a
file system backup of the C: drive being performed via the TSM B/A Client.
When it failed the following messages were logged by RM:

24-Jun-2009 15:09:41 xxxxxxxxxx 100711 INFORMATION: The SQL BACKUP command
completed. Details [Microsoft][ODBC SQL Server Driver][SQL
Server]Processed 0 pages for database 'XXX'.
24-Jun-2009 15:09:41 xxxxxxxxxx 100711 INFORMATION: The SQL BACKUP command
completed. Details [Microsoft][ODBC SQL Server Driver][SQL Server]BACKUP
DATABASE successfully processed 0 pages in 10.161 seconds (0.000 MB/sec)..
24-Jun-2009 15:09:41 xxxxxxxxxx 000711 ERROR: Microsoft Volume Shadow Copy
error: The I/O writes cannot be held during the shadow copy creation
period. Please verify the load and configuration of storage array and try
again.
24-Jun-2009 15:09:41 xxxxxxxxxx 026202 ERROR: Storage Services operation
waitVSSCompletion failed with an error as follows: Wait Snapshot
completion failed.
24-Jun-2009 15:09:41 xxxxxxxxxx 026084 ERROR: Storage Services operation
processExecute failed with an error as follows: Storage Services has
terminated with an error.

With the help of some excellent analysis from an EMC support
representative, my colleague was eventually able to determine that the
problem was due to the location of the shadow copies of the C: drive.
Using the VSSADMIN LIST SHADOWSTORAGE command during the TSM file system
backup, it became apparent that, by default, the shadow copies of the C:
drive were being stored on the P: drive.The choice of the P: drive for the
shadow copies was consistent, but probably fairly arbitrary taking into
account for example free space. However the presence of the shadow copy on
P: appeared to be interfering with the EMC hardware provider's ability to
snap the LUN within the array.

The solution was simple - we confined the shadow copies of the local disks
to local disks by defining shadow copy storage associations thus:
VSSADMIN ADD SHADOWSTORAGE /FOR=C: /ON=D:

Regards
Neil Schofield
Yorkshire Water

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