Re: [Veritas-bu] Dedupe ratios and checkpoint backups
2011-09-08 07:21:25
I think the question was: where is that
file located when it is created, and does it then get backed up by the
job doing the backup itself?
From:
| David Stanaway <david AT stanaway DOT net>
|
To:
| veritas-bu AT mailman.eng.auburn DOT edu
|
Date:
| 09/07/2011 09:11 PM
|
Subject:
| Re: [Veritas-bu] Dedupe ratios and checkpoint
backups
|
Sent by:
| veritas-bu-bounces AT mailman.eng.auburn DOT edu |
Checkpoints create a new file for each checkpoint.
On 9/7/2011 1:17 PM, Rusty Major wrote:
I have always understood
it that Checkpoints were saved in a log on the client and, therefore, wouldn’t
affect dedupe ratios at all. I haven’t ever verified that, nor did a quick
search yield anything.
-Rusty
From: veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu]
On Behalf Of Lightner, Jeff
Sent: Tuesday, September 06, 2011 3:23 PM
To: scott.george AT parker DOT com;
veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] Dedupe ratios and checkpoint backups
Haven’t done any comparisons
but we use checkpoint for our big ERP DB (near 6 TB) backup and still get
good compression ratios. There is nothing that has made me think
I need to look at it or tweak it to get better. I’d say the benefit
of not having to restart a huge backup from scratch offered by checkpoints
would outweigh deduplication ratio issues unless you have infinite time
to run backups.
From: veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu]
On Behalf Of scott.george AT parker DOT com
Sent: Tuesday, September 06, 2011 3:06 PM
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] Dedupe ratios and checkpoint backups
To answer your question, we tested both the
NBU 5000 (Symantec) and the DD860 (Data Domain) and the differences couldn't
be more stark. I was using a 30 minute checkpoint interval. I
never achieved anything better than 15:1 from the NBU5000 (which isn't
bad). The DD860 hit 39:1 at the time I disabled all of the policies.
This was running daily full backups on an array of different servers
(DB2, Windows file servers, UNIX file servers, and Siebel app servers)
over the course of 2 months.
The NBU5000 is a fixed block device, the DD860 a variable block device.
There is no way of knowing if checkpoints were the culprit for the
NBU5000 getting the lesser ratio, but it does present a plausible theory.
If at all, this would probably affect fixed-block solutions more than the
variable-block ones. The variable-blocked solutions would continue
to look for identical blocks, but in different positions of the data stream.
Just wondering if anyone has done testing or seen documentation (from any
dedupe vendor) regarding the usage of enabling checkpoints on backups that
are being deduplicated? I would think that the introduction of checkpoints
every X minutes into the datastream would interrupt the continuity of the
data and make it seem more unique thus negatively affecting dedupe ratios
but I’m wondering by how much. Most, if not all, of the variable
length guys have the ability to ‘re-align’ themselves to the start of
the files so I would think it might be more pronounced on large files vs
your average server but I’m just thinking out loud.
Anyone seen a recommendation or actually tested themselves?
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www.barclaycardus.com
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