Hi Phil,

Retrospect's verification checks the entire system, from source data, to
backup media, to restore, and everything in between. In fact, for its
verification pass, Retrospect uses the same routines that are used for
restores -- the only difference is that, at the last moment, instead of
being written back to the source, the data is compared with the original,
then discarded.

Tape drive "read-after-write" verification only tests to see that the bits
read off the tape match the bits in the buffer. It doesn't check to see that
the data got where it was going without corruption or change.

Retrospect's verification has ferreted out things like bad routers that
corrupt one in 500,000 packets. That may not sound like a big problem, but
if you can't successfully restore a file because it happened to be one that
got corrupted, that's a concern.

I hope this makes sense. We do a lot of things in Retrospect purely from a
restore point of view. That's why it's the most reliable backup software

Eric Ullman
Dantz Development 

> Subject: Verification Pass on Travan NS
> My understanding is that Travan NS does a read immediately after doing a
> write and then automatically rewrites any bad blocks.  I noticed that
> Retrospect still does a verify pass when used with a Travan NS 20 drive.  Is
> it up to the user to turn verification off?  And is there any reason why this
> wouldn't be a good idea?
> Phil Geller
> WorkingMacs

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