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Restore - consistency checker

 
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Tuval
Occasional Contributor

Restore - consistency checker

Is there any tool that actually checks for the consistency of the data when a recovery process is finished, to make sure that the restored system is at exactly same state as the backuped one?
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Brian M Rawlings
Honored Contributor

Re: Restore - consistency checker

I don't know of any tools which purport to be able to do this. I suspect it is more a procedural issue than a tool-needed issue.

For instance, it would be important to occasionally check your backups to make sure you can restore any and all data if necessary. This means a procedure that you do every so often, which probably includes a restore or a 'mock restore', at least proving that the data is on the backups, and hopefully proving that a restore will put it back where it goes.

Expand this to include procedures (and a test schedule for proving them out) for checking any remotely replicated data (hot site, etc), testing your system recovery tapes (make_tape_recovery, system image backups), testing any HA failover setups (MC/Serviceguard), and even testing Hardware and network failover schemes you have in place. This can be quite a list, some done quarterly, some annually, and is virtually a discipline of its own withing the 'sysadmin' job.

As far as ways to check that restored data is the same as what it was when it was backed up, I would suggest taking a checksum of some or all of your directories, doing a backup, doing the restore, then running the checksum again to prove that everything is the same, right down to the last byte. This would take some fiddling with, since some things might show up differently simply due to the fact that time has passed, and timestamps (etc) may not be identical.

There are other ways of double-checking data (tar it all to a tar-ball, and check the tarballs against each other, etc), plus there is the backup provider asserting that data they backup gets exactly restored (you might look into THEIR user forums to see if users have complaints or issues with restores.

I hope this provides some ideas for you, since I can't help with any specific tool to do this.

Best Regards, --bmr
We must indeed all hang together, or, most assuredly, we shall all hang separately. (Benjamin Franklin)
paul courry
Honored Contributor
Solution

Re: Restore - consistency checker

This is usually handled by CRC checksums embeded in the storeage medium. If there is a problem, you'll be told.

I would suggest that you occassionally restore a few files at random and compare them to what was there originally (just rename the existing file first). This is a common practice in most professional IT shops and ensures that the tape drive has not gone south in the interim.