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Deduplication when using SQL Server backup compression

A quick question about using NetBackup with compressed SQL Server backups.

Our backups infrastructure consists of NetBackup v7.6 and NetBackup 5230 appliances. Our SQL server estate is a mixture of SQL Server versions 2005-2012 on Windows 2003-2012.

We've noticed that the deduplication ratio (as reported by backup jobs in Netbackup Activity Monitor) for compressed SQL backups is 0% (we experimented with the NetBackup SQL Agent and also standard flat file backups).

Now we weren't expecting to get much deduplication out of a compressed SQL Server backup - but it was a suprise to get nothing at all. Previous tests performed on other deduplication platforms (Exagrid and Windows native 2012 deduplication) showed that a noticeable (albeit much lower rate compared with uncompressed backups)  deduplication level of about 4:1 was possible with compressed SQL Server backups.

So my question is - is this a configuration issue on our NetBackup infrastructure - or is there a technical\design reason why the deduplication of compressed SQL Server backups is not available in NetBackup?

Regards

Terry

1 Solution

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Accepted Solution!

Compression provided by the

Compression provided by the native tool is great if you're not using enterprise class backup products e.g. you're backing up to some local drive or network share. You've invested thousands in the appliance infrastructure, let it do its job. You should get much higher compression values that you quoted above. In general I see SQL giving more than 90%, i.e. 10x.

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Any DB compression should be

Any DB compression should be switched off when backing up to dedupe storage.

See Symantec NetBackup™ Appliance Capacity Planning and Performance Tuning Guide DOC6745 - Chapter 5:  Microsoft SQL
Table 5-2 Best practices to perform SQL server backups

Look at all of the recommendations in this section.

Accepted Solution!

Compression provided by the

Compression provided by the native tool is great if you're not using enterprise class backup products e.g. you're backing up to some local drive or network share. You've invested thousands in the appliance infrastructure, let it do its job. You should get much higher compression values that you quoted above. In general I see SQL giving more than 90%, i.e. 10x.

View solution in original post

You likely will never see per

You likely will never see per job deduplication when backing up anything compressed.  You may get some single instancing at the dedupe pool.  I'd question the accuracy of any dedupe technology telling you it can deduplicate a compressed file.  The math doesn't work for that to be the case.