Date: Mon, 14 Mar 2005 10:30:25 -0500 (EST) From: Jerry McAllister <jerrymc@clunix.cl.msu.edu> To: lorenl@alzatex.com (Loren M. Lang) Cc: freebsd-questions@freebsd.org Subject: Re: What's the easiest way to do a backup and verify? Message-ID: <200503141530.j2EFUQj15904@clunix.cl.msu.edu> In-Reply-To: <20050313082656.GB18080@alzatex.com> from "Loren M. Lang" at Mar 13, 2005 12:26:56 AM
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> > > > Is there an easy way to combine a backup and verify when doing backups > > > with dump? > > >=20 > > > 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. > >=20 > > 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. > >=20 > > 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 > No, because the condition of the files that you are dumping the second time is different from the first time. That is the same problem as using the verify option with dump. The only way to do it would be to do your dumps on a completely quiescent system - single user mode maybe. Most places cannot afford to make file systems completely unavailable for periods of time long enough (several hours, up to a couple of days) to allow dump to be run twice without any changes being made to the file system. ////jerry > Though I don't have much experience with either dump or tapes to verify. >
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