Re: What's the easiest way to do a backup and verify?

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Date: Sun, 13 Mar 2005 00:26:56 -0800
To: Jerry McAllister <jerrymc@clunix.cl.msu.edu>

On Mon, Mar 07, 2005 at 09:47:31AM -0500, Jerry McAllister wrote:
> >
> > Is there an easy way to combine a backup and verify when doing backups
> > with dump?
> >
> > On Windows NT it's just a matter of checking a box. I seem to recall
> > the last time I looked into this on UNIX there was no easy way to
> > accomplish a verify operation for a backup, but perhaps things have
> > changed with FreeBSD 5.3 (?).
> >
> > I've never had a problem with backup (I backup to DAT tape), but I'd
> > feel better if every backup was followed by a verify to make sure the
> > tape is readable.
>
> Actually, if used frequently for backups - such as every day, DAT is
> notoriously prone to failure. So, it is a good idea to check dumps
> made to DAT. Unfortunately, there is not a reasonable way to
> automatically do it. There is a verify, but it cannot work on a
> running system, because it compares files (inodes) on the tape back
> to the ones on disk. Any changes mean an error, even if it was a
> real change in the file between the time it was written and the
> time it was read back.
>
> The only real thing you can do is to read back the tape and look
> for a couple of files with fairly high inode numbers for each file
> system dumped. If you can read them, you can assume the tape
> is readable.

I'm not very familiar with tapes, but I think that the dump is written
straight out to something like /dev/st0 right? So then wouldn't a
second dump of the same snapshot diffed to the tape device be a good for
a verify?

Position tape at beginning of dump
dump / | diff - /dev/st0

Though I don't have much experience with either dump or tapes to verify.

>
> ////jerry
>
> >
> > --
> > Anthony
> >
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