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From: verber@pacific.mps.ohio-state.edu (Mark Verber)
Newsgroups: comp.unix.admin
Subject: Re: SUMMARY: Backup while in multi-user mode
Message-ID: <VERBER.91May21181220@avalon.mps.ohio-state.edu>
Date: 21 May 91 22:12:20 GMT
References: <1991May20.123129.14433@forwiss.uni-passau.de>
	<1991May20.204327.17694@erg.sri.com> <690@silence.princeton.nj.us>
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Organization: Ohio State University; Physics Department
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In-reply-to: jay@silence.princeton.nj.us's message of 21 May 91 07:30:05 GMT

In article <690@silence.princeton.nj.us> jay@silence.princeton.nj.us (Jay Plett) writes:

   Ah, there's the point.  If you can _risk_ losing one or two days work,
   then do daily level 0s on live filesystems.  This is the beauty of
   Exabytes--it is feasible to do so.  If a tape is bad at restore time,
   toss it and go back a day.  If that one is bad, go back another day.
   The risk dimishes greatly with each day you go back.

Don't bet on it.  Lets say that you are running your backups from cron
-- most of us with exebytes do.  Suppose you have something else
running in cron, or like my site, a user process that runs for days at
a time which does all sorts of i/o.  Lets say the i/o going on when
dump runs happens to be doing just the wrong kind -- eg your dump is
corrupted.  Every dump you take could be screwed -- redundancy didn't
win you much, did it.

I understand the desire to do dumps on active file systems for daily
incrementals... but what do people have against doing the level 0
dumps in single user.  Can't you afford a few hours downtime in the
middle of the night once a month to insure a clean dump?  You don't
even have to be around while the dumps are running with exebytes since
you don't have to change tapes or if your full saves won't fit on the
drive(s) you have, get a stacker.

sigh,
mark