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From: bzs@BU-CS.BU.EDU (Barry Shein)
Newsgroups: net.unix-wizards
Subject: Backups to disks
Message-ID: <4516@brl-smoke.ARPA>
Date: Fri, 10-Oct-86 12:47:14 EDT
Article-I.D.: brl-smok.4516
Posted: Fri Oct 10 12:47:14 1986
Date-Received: Sat, 11-Oct-86 20:39:30 EDT
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You can certainly do backups to disk, you just shift your risks and
costs.

Note that disks are much more subject to various failures than tapes
(not that tapes are perfect, not by any means.) One major reason for
this is that your disk is constantly spinning and accessible (unless
you turn it off and on which can make things worse, dismounting it
helps of course, but not at all with mechanical failure.) Your tapes
can be locked away someplace, safe from power surges, software errors
and head crashes (saf*er* anyhow.)

One possible compromise is to automate backups to a spare disk
(assuming they really fit) and then backing *that* disk up to
tape in one fell swoop which might be more efficient than running
tapes and operators all over the place to different systems (this
is particularly true if you could run the dumps over a network to
the local disk.)

It really all comes down to a systems analysis, how important are your
backups to you? How disasterous would it be if you lost one?  If you
lost a series of them (all on one disk)? How much data are you backing
up? Does it fit on one disk? How long do you keep backups? What are
you promising your user's as far as file retrieval etc goes?

There's no "answer", it's a complicated question.

I keep hoping the "answer" will be inexpensive CD technology which
should be the best of both worlds (on-line, operatorless, fairly large
and robust, inexpensive*, removeable media.)

I keep waiting though.

	-Barry Shein, Boston University

* Not yet, this is the major problem.