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From: preece%mycroft@gswd-vms.arpa (Scott E. Preece)
Newsgroups: comp.unix.wizards
Subject: Re: On backups
Message-ID: <7336@brl-adm.ARPA>
Date: Tue, 12-May-87 11:25:20 EDT
Article-I.D.: brl-adm.7336
Posted: Tue May 12 11:25:20 1987
Date-Received: Fri, 15-May-87 00:43:48 EDT
Sender: news@brl-adm.ARPA
Lines: 39


  Derek Terveer:
> Even our little machines (two vax 11/780s) doing development work
> generate an *average* of ~45MB per day each of incremental saves.  There
> are definitely days when our incremental fs overflows!
----------
I suspect, though, that many sites don't generate nearly that much
SOURCE material (if you don't bother saving .o files and various other
temporaries your REAL daily save load may go way down).

Note also that keeping the incrementals online for a month is just
a convenience; most of the advantages of the idea are still obtained
if you do the incrementals and one other partition daily to a big
drive and then just do a daily level 0 on that one drive.  Restoring is
more of a pain, but the saving in tape handling is still there.  If you
keep an index of what went on what incremental you ease the restore
problem enough.

  Don Speck:
> Some consultants here did their backups by periodically copying the
> active disk pack to a backup pack.  One night, the active pack crashed
> in the middle of a backup.  They were left with half of an image copy of
> the filesystem, which is completely useless; they lost the entire
> sources and compilers for their proprietary operating system.  A year
> later, they are still stuck with making binary patches.
> 
> So it doesn't require two simultaneous head crashes to lose a lot.
----------
But that's a much less safe procedure than was suggested.  Doing a
direct copy-over backup without using alternating backup disks is
obviously dumb.  Assuming he's doing daily incrementals on his one
backup drive, the original poster is never at risk for more than a
day's backups.

-- 
scott preece
gould/csd - urbana
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