Veritas-bu

Re: [Veritas-bu] Netbackup verify at write time

2008-07-23 08:07:07
Subject: Re: [Veritas-bu] Netbackup verify at write time
From: "Ed Wilts" <ewilts AT ewilts DOT org>
To: dave.markham AT fjserv DOT net
Date: Wed, 23 Jul 2008 06:45:59 -0500
On Wed, Jul 23, 2008 at 5:44 AM, Dave Markham <dave.markham AT fjserv DOT net> wrote:
Guys management here are fussing around how are we sure backups are
successful or they can be restored from without doing an actual restore.
 
There is no sure fire way.
 
I know the only sure fire way of knowing a backup is fine is performing
a restore, but unless a full restore is done (which has its own problems
of space etc) then what other assurances are there?
 
To a certain extent, you have to trust the hardware.  Even if you do a test restore, you are still hoping that the tape doesn't fail between your test restore and an actual restore.
 
In order for a verification run to complete successfully, the file must not change between the time you wrote it and the time you went to verify it.  After all, if the file changed, how will you know if the verify is failing because the file changed, or because the data was read incorrectly from the tape?  If you are backing up read-only file systems, you can verify, but other than that, you're really out of luck.
 
The purpose of a test restore is not just to validate the media - it's also to validate that you're actually backing up the stuff you need to restore an application.  Even the though the backup is physically good, if you forgot to back up a required file or a cron job that was supposed to quiesce a database didn't actually do so, you're not going to have anything useful.  We caught this in our testing - a cron job that compressed and moved archive logs ended up setting old file dates on the tarball - incremental backups based on file dates didn't pick up the files and they never got to tape.
 
Test.  Repeat regularly.
 
Netbackup 5.0MP7, 6.0MP4 on a mixture of Solaris 9 and 10
 
You may want to let management know that the you're more likely to be able to do a succesful restore using modern, supported software.  5.0 is no longer supported and if you do ever have a restore issue, Symantec is not likely to want to help you. 
 
   .../Ed

--
Ed Wilts, Mounds View, MN, USA
RHCE, BCFP, BCSD, SCSP, SCSE
mailto:ewilts AT ewilts DOT org

If I've helped you, please make a donation to my favorite charity at http://firstgiving.com/edwilts
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