Veritas-bu

Re: [Veritas-bu] Question for NetBackup 7.0 Dedup user OR Data Domain users

2010-08-24 17:24:59
Subject: Re: [Veritas-bu] Question for NetBackup 7.0 Dedup user OR Data Domain users
From: Ed Wilts <ewilts AT ewilts DOT org>
To: "Alley, Chris" <CAlley AT kforce DOT com>
Date: Tue, 24 Aug 2010 16:24:51 -0500
On Tue, Aug 24, 2010 at 4:09 PM, Alley, Chris <CAlley AT kforce DOT com> wrote:

We are looking to change our backups to a disk based deduplication solution, and 2 of our options are to utilize NetBackup 7.0’s built in dedupe (Client and Media server) or to put a Data Domain box in.  I wanted to see if I could get some real world feedback on what you guys have been seeing in terms of dedupe rates, performance, etc.  For example Data Domain claims we would only see about 5:1 dedupe rate using NetBackup, which seems quite a bit lower than what I would expect….and of course they claim they would get about 20:1.  I realize that all data is different, which is why I have hopes that several people will reply with what they are seeing.  Thanks for your time!


De-dupe ratios depend on a LOT of things with the primary one  being how many generations of backups you're keeping.

Assuming the data changes very, very little:

If you have a weekly full and keep them for 5 weeks, you'll get your 5:1 ratio. 
If you do a semi-annual full and keep 2 copies, you'll get a 2:1 ratio.
If you do a weekly full and keep them for a year, you'll get a 52:1 ratio.

If the data changes a lot and you end up with random data every day, your de-dupe ratio will likely suck.  We work with a lot of TIFF images here and get lousy de-dupe ratios.

We've got some data where we get excellent de-dupe and a lot of data where we get close to zero de-dupe.  The vendors all price their products assuming a high de-dupe ratio with the assumption that de-duping your data is cheaper than buying disk.  For some data sets, that's actually a poor assumption. 

Symantec offers optimized synthentics in conjunction with their de-dupe.  Don't rule this out as a very worthwhile benefit - imagine a single full and then incrementals for life...

Ed Wilts, RHCE, BCFP, BCSD, SCSP, SCSE
ewilts AT ewilts DOT org

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