Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!ll-xn!cit-vax!mangler
From: mangler@cit-vax.Caltech.Edu (System Mangler)
Newsgroups: comp.unix.questions,comp.sources.wanted
Subject: Re: Backup Utilities for Unix
Message-ID: <2653@cit-vax.Caltech.Edu>
Date: Mon, 11-May-87 06:53:08 EDT
Article-I.D.: cit-vax.2653
Posted: Mon May 11 06:53:08 1987
Date-Received: Wed, 13-May-87 01:14:30 EDT
References: <1308@ci-dandelion.UUCP> <4360@videovax.Tek.COM>
Organization: California Institute of Technology
Lines: 18
Keywords: system management backups dump restore
Summary: "live" backups
Xref: mnetor comp.unix.questions:2246 comp.sources.wanted:1139

In article <4360@videovax.Tek.COM>, stever@videovax.Tek.COM (Steven E. Rice, P.E.) writes:
> One feature
> that would be invaluable is the ability to back up the filesystem while
> the machine is loaded with users and running.

This is not generally workable.  Consider a filesystem with three
directories, A, B, and C.  After the hypothetical backup program
finishes looking through A, and is busy looking through B, some
user moves a file from C to A.	It will not be backed up.  You
can also work it the other direction, and get two copies of the
file.

I understand that some Burroughs operating system solves this by
putting its filesystems into "snapshot mode" for the duration of
the backup, where all files/directories to be backed up are treated
as copy-on-write.  Requires adequate free space...

Don Speck   speck@vlsi.caltech.edu  {seismo,rutgers,ames}!cit-vax!speck