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Support

CPS Snapshot sizes

Richard_Harber
Level 2

‎11-03-2006 05:38 AM

We have deployed a CPS server in a multi-server Windows 2003 R2 environment. At one point we were pulling in about 300GB of data to the CPS server. However, due to the size of the snapshots, we trimmed back the back up jobs and the frequency of snapshots. Currently,.the backup destination is a mere 50GB of data. We have snapshots set for every 4 hours from 8am to 6pm, plus one end of day. The first and last snapshots of the day are huge! Normal snapshot is about 6Mb - 10Mb if you used VSC; End of day is 27GB (yes GB) for yesterday; day before was 17GB. During day snapshots range in size from 1GB to 3GB. We are not making changes in files which would dictate these files should be this big. Again, if you do a VSC snapshot for the same period, they are much much smaller.

Anyone have any idea what is going on and why these snapshots are so large?
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1 REPLY 1

Peter_Parker
Level 3

‎11-08-2006 05:36 AM

There are a few things to remember when considering the size of a snapshot.

1. The snapshot is of the entire volume where the backup destination resides and not just a snapshot of the Backup Destination folder. So in order to minimize the amount of data in a snapshot place the Backup Destination on a drive dedicated for that purpose only. Otherwise extraneous data will be present in the snapshots. This is a characteristic of VSS rather than CPS.

2. Snapshots will always vary in size depending on the presence of previous snapshots and the amount of changed data (on the entire volume) from the previous snapshot. So the first snapshot is a full and the one 4 hours later will be the data that changed since that time. If a full is somehow deleted, for whatever reason, then a new full will most likely be required.

Your example of using VSS to take a snapshot for comparison most likely isn't a valid test because the snapshot you take in your test will still be based on previous snapshots.

3. Depending on your CPS Backup Schedule you may not need to be taking as many snapshots as you have configured CPS to take.

Take a look at this technote:
http://support.veritas.com/docs/281173
Backup Exec Continuous Protection Server (CPS) Snapshots are being deleted by Windows 2003 before reaching the age at which CPS will automatically delete them.

The title may not seem relevant to you but there are some best practice guidelines.
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