I posted this just over 2 weeks ago and haven't seen it come through, so
here it is again.
My original question was:
We are currently looking at our backup strategy and whether
it is still necessary or recommended to do our level 0 backups
while the machine is in single user mode.
Have any of you done level 0 backups in multi user mode? How have
they gone? Have you had any corruption when you have come to
restore some files?
I'd like to hear recommendations and experiences for and against
doing the level 0 backups in multi user mode. I'll summarise my findings.
Thanks,
Sue
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A very big thankyou to all of you who replied.
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SHORT SUMMARY - detailed one following
I've had very mixed feedback. Quite a number saying they have been doing
level 0's in multi user mode for years and had no problems at all in
restoring file systems. A few however have had problems and use single
user mode. So I guess it is still a matter of preference and whether you
feel your systems are fairly quiet at a particular time.
Quite a number do the level 0s in multiuser but also do a couple of
single user dumps per year as a backup.
The main consensus I got was that doing level 0s backups in multi user
mode is a risk, in that the files you are backing up may be active. Most
felt it was worth the risk as bringing a machine down to single user mode
was disruptive to the users and by picking a low use time you minimise
the risk. Someone also pointed out that you can't be 100% sure that a
backup will be okay even in single user mode.
We personally have decided to continue to do level 0s in single user
mode as we bring the machines down remotely during the early hours of the
morning and thus it causes very little disruption to our users. We are a
research and teaching site and often have some users working thru the wee
hours of the morning, so there really is no time when we can guarantee
that there won't be someone doing something on our systems. We have had a
few instances of late where system discs have crashed and had to be
restored from scratch.
So far there have been the following responses
40 level 0s fine in multi user mode - never had any problems
10 be cautious with level 0s in multi user mode
1 recommend do level 0s in single user mode
1 never do level 0s in multi user mode - always do them in single user mode
Take your pick as to what you policy you pursue. It really comes down to
preference, risk and convenience.
Sue
PS If any one would like all the replies I can tar them up for you. There
are some interesting suggestions and points.
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DETAILED SUMMARY
A. level 0s fine in multi user mode - never had any problems
---------------------------------------------------------
1 Todd Pfaff <todd@flex.eng.mcmaster.ca>
2 Mark Prior <mrp@itd.adelaide.edu.au> - although do single user mode level
0 just before upgrade OS
3 Jeffrey Marans <jeff@erie.irc.nrc.ca>
4 sckhoo@emtds1.nsc.com (Swee-Chuan Khoo)
5 Johannes Grosen <grosen@isc.cs.ndsu.nodak.edu> - get a baseline copy in
single user mode - Remember there are no guarantees even in single
user mode.
6 Peter Farmer <Peter.Farmer@cs.anu.edu.au> - the inconvenience of bringing
a system down justifies the risk of doing dumps in multi user. They work
99% of the time.
7 david@slag.capmkt.com (David Mostardi) - very quiet system at 3am.
8 Martin Achilli <ACHILLM@IMIHSRA.BITNET> - done 5 crashed disc restores
with no problems.
9 cciolori@tatca.tc.faa.gov (Chris Ciolorito)
10 abailey@adams.com (ALLEN K. BAILEY, MECHANICAL DYNAMICS, INC.)
11 John A. Murphy <jam@philabs.Philips.COM>
12 John Murray <John.Murray@germany.eu.net>
13 gnats-admin@atc.ll.mit.edu (Rick Lloyd x4841 ) - I have been running
backups here on several different systems for 8 years and NEVER been
unable to restore when needed. Note that this is not the same as
guaranteeing all backups are readable but...
14 Armin.Weber@bk.sel.de (Armin Weber)
15 Steve Elliott <se@comp.lancs.ac.uk>
16 Reinhardt Quelle <quelle@netcom.com>
17 raoul@MIT.EDU - do in single user mode only before OS upgrade
18 dburwell@telecom.telecom.com (David Burwell (7929))
19 bern@kleopatra.Uni-Trier.DE (Jochen Bern)
20 lcollera@amgen.com (Lori Colleran)
21 p.elliott@trl.oz.au (Paul Elliott)
22 JIMMY <sjs@solomon.technet.sg>
23 kumeda@tds.com (ANDY KUMEDA)
24 seanw@amgen.com (Sean Ward)
25 Mike Raffety <mike_raffety@il.us.swissbank.com>
26 celita@taux01.nsc.com
27 libby.thick@aea.orgn.uk (Elizabeth Thick x2688)
28 szh@zcon.com (Syed Zaeem Hosain)
29 Eckhard.Rueggeberg@ts.go.dlr.de (Eckhard Rueggeberg)
30 Nick Murray <nick@computing-science.aberdeen.ac.uk>
31 jpl@allegra.att.com (John P. Linderman)
32 the guru dude <bryan_helvey@wiltel.com>
33 Brad Burdick <bburdick@radio.com>
34 x092306@hyperion.LANL.GOV (Jerry Weber C-8/IS-5)
35 jb@highscc.uucp (Jon Bowman)
36 ostel@kaman.com (Mark Costello)
37 minieri@mars.tsdatl.rockwell.com (Joe Minieri)
38 rgreen@roch803.mc.xerox.com (Russ Green)
39 Larry Nelson <nelson@zorro.cecer.army.mil>
40 Mike Richman <richman@reepicheep.gcn.uoknor.edu>
B. be cautious with level 0s in multi user mode
---------------------------------------------------------
1 Todd Kover <kovert@cs.UMD.EDU> - do a couple of single user mode dumps per year
2 Mike Cross <cross@engfs.med.ge.com> - umounts partitions as he backs
them up, so that the file system is not being accessed during the dump.
3 rich_b@oldham.gpsemi.com (Richard Bogusz) - you want the disk being
backed up unmounted.
4 symanski@gold.nosc.mil (Jerry Symanski - NRaD Code 761) - a matter of
probabilities.
5 "Peter A. Starceski" <starcesk@noc.hfh.edu> -
Some of the key issues that you'll need to
deal with is (1) to make sure no processes are running that are owned by
users (e.g. if any users are logged in) --- I think that there is public
domain software to terminate logins after a specific time period --- and
(2) fsck each partition device successfully before backup.
6 rosi punton <rosi@redgum.ucnv.edu.au> -
i doubt that the reasons for backing up in single user mode have changed
(so to avoid backing up open files) but we cannot afford to down our
machines to backup so we risk it in multi-user mode.
7 perryh@pluto.rain.com (Perry Hutchison)
leaving the machine in multi-user but touching /etc/nologin at the start
and removing it when done just in case anyone might try to dial in
during the backup.
8 admin@gilligan.UCSD.EDU (System Administrator)
9 Ted Rodriguez-Bell <ted@ssl.Berkeley.EDU>
10 vogelke@c-17igp.wpafb.af.mil (Contr Karl Vogel)
C. recommend do level 0s in single user mode
---------------------------------------------------------
1 phaedrus%triples@triples.math.mcgill.ca (Phong Co)
D. never do level 0s in multi user mode - always do them in single user mode
---------------------------------------------------------
1 kam@math.tulane.edu (Katherine Hosch) - I have done it, and restoration
isn't pretty.... I always do level0 in single-user mode now.
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Different systems used to do dumps
-----------------------------------
DEC's version of Legato Networker
Mark Prior <mrp@itd.adelaide.edu.au>
amanda
Todd Kover <kovert@cs.UMD.EDU>
Martin Achilli <ACHILLM@IMIHSRA.BITNET>
backup copilot
david@slag.capmkt.com (David Mostardi)
John Murray <John.Murray@germany.eu.net> -
Get Backup Copilot from Sun. (it's not a wild package but it works)
We use it combined with Amanda (Free :-) ftp from cs.columbia.edu)
It includes a modified version of dump and restore that allow safe online
dumps. It seems to work fine so far (approx 1 year intensive use), just try
to chose a calm time for level 0.
This archive was generated by hypermail 2.1.2 : Fri Sep 28 2001 - 23:08:58 CDT