Path: utzoo!utgpu!attcan!uunet!lll-winken!ames!mailrus!ncar!tank!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.unix.questions
Subject: Re: Dump in multi-user mode?
Message-ID: <15643@mimsy.UUCP>
Date: 26 Jan 89 13:06:08 GMT
References: <352@lilink.UUCP> <780@sering.cwi.nl>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 26

In article <780@sering.cwi.nl> fmr@cwi.nl (Frank Rahmani) writes:
>... Under BSD4.[23] and SunOS3.5 we do dumps for years in multiuser
>mode with typically up to 50 users on a machine without any problem
>whatsoever.

I think it more likely that you have done this without *noticing* any
problems, or perhaps better phrased, without having anything go wrong
unrecoverably.

I know of no Unix systems with backup procedures that are immune to
errors if run on an active file system.%  It is easy to engineer
disasters (major in older versions of 4BSD dump/restore, minor in new
ones), and Murphy is there to do it when you need it least.
Nonetheless, the benefit of multiuser backups is not inconsiderable.
You must decide for yourself whether the advantage outweighs the risk.
In the CS Department here, we compromise by doing biweekly level 0
backups in single user mode, and daily backups multiuser.
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% Although Kirk has been heard to mutter something about `fsfreeze'.
-----

(Incidentally, while calculating risks, it is worth considering
operator error during backups and/or restores.  It does happen.)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris