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Physical compare verify

Created: 23 Apr 2014 | 5 comments
Spencer Simpson's picture
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A few years ago, I asked a question about verify jobs in the Bacup forum

https://www-secure.symantec.com/connect/forums/so-...

and got a real schooling about Verify jobs in Backup Exec. 

I thought I'd introduce a feature idea based on the incorrect notion I had about Verify - that being a physical comparision between a source and a backup copy.

In a D2D2T or tape-to-tape copy, it might be worthwhile to go back and compare the actal data in the source with the data in the copy.

It's not a tenable concept for a live server (I suppose you could always compare a copy with the source snapshot used to create the copy) but if the source is known to be stable, and the need for absolute certainty exceeded the time penalty incurred (e.g. shipping a strategic product out to a customer), it might be worth having that possibility. 

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pkh's picture

How can you be sure that the source have not changed?  If the comparison fails, what are you going to do?

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Spencer Simpson's picture

"The source is known to be stable" as specified in the original post. That's the working assumption. Perhaps no-one has write access.  Perhaps you are comparing the disk backup set to the duplicate on tape.   If the comparison fails, that would mean there is a hardware problem.  So you replace the hardware.

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CraigV's picture

...based on a comparison with a snapshot (and ONLY a snapshot) that mustn't get deleted until the verify has either run (or not run if Verify isn't selected), it might work. However, I don't know of any other vendor that does it this way.

Thanks!

Alternative ways to access Backup Exec Technical Support:

https://www-secure.symantec.com/connect/blogs/alte...

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Spencer Simpson's picture

I should have said this when I saw it:  It needn't only be a snapshot. You could compare a backup set on disk with its duplicate on tape. 

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Spencer Simpson's picture

Granted, this whole thing is just a flight of fancy.  And something with a limited (albeit very important) applicability.

The probability of flipping one bit somewhere and then another bit somewhere else to make the checksums the same is low, but you never know.   

The easiest bit to implement would be doing this after duplicating an existing backup set, because the original source backup set is there and stable. Assuming tape is finickier than disk. 

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