schemers@vela.acs.oakland.edu (Roland Schemers III) (03/17/90)
Hello! I have a question about using 'dump'. How dangerious is it to
dump an active file system? That is, dumping a file system that is
mounted, and while the system is in multi-user mode? I have gotten
various replies from DEC, ranging from "It might corrupt the whole dump",
or "Only the active files will be messed up".
For a monthly or weekly dump I see no problem with bringing the system
down to single user, but every day to do incrementals seems a bit
drastic.
Roland
ps. we are currently using opser, and doing daily (level 9), weekly (level 5),
and monthly (level 0) dumps, bringing the system down to single user mode.
--
Roland J. Schemers III Systems Programmer
schemers@vela.acs.oakland.edu (Ultrix) Oakland University
schemers@argo.acs.oakland.edu (VMS) Rochester, MI 48309-4401grr@cbmvax.commodore.com (George Robbins) (03/19/90)
In article <384@vela.acs.oakland.edu> schemers@vela.acs.oakland.edu (Roland Schemers III) writes: > Hello! I have a question about using 'dump'. How dangerious is it to > dump an active file system? That is, dumping a file system that is > mounted, and while the system is in multi-user mode? I have gotten > various replies from DEC, ranging from "It might corrupt the whole dump", > or "Only the active files will be messed up". > > For a monthly or weekly dump I see no problem with bringing the system > down to single user, but every day to do incrementals seems a bit > drastic. There's no really good answer to this question. If you want dump that are guarenteed to be restorable without hassle, do *all* of the either standalone or with the filesystem unmounted. Many sites compromise by doing the critical (level 0, weekly) dumps in standalone mode and doing the daily incrementals while the system is up, ideally during a low activity time period. This approach means that you can get the bulk of the files back without difficulty, but you may have to dick around with multiple daily tapes and/or partial restores to get everything exactly current. Most of your user request for file restores will come from a recent daily incremental dump and restoring individual files always seems to work. There are "improved" versions of dump floating around that are supposed to be more rugged in terms of working on active filesystems, however I haven't heard of one ported to Ultrix. You can also do something like getting an 8mm drive and doing daily full tar dumps in the background. The tar format is stupid and less prone to the kind of problems that dump/restore encounters when things change during the dump. The Gnu version of tar also has provisions for doing incremental tar dumps, which might give you the best of both worlds. For System V fanatics, cpio is just about as stupid as tar in this respect. 8-) -- George Robbins - now working for, uucp: {uunet|pyramid|rutgers}!cbmvax!grr but no way officially representing: domain: grr@cbmvax.commodore.com Commodore, Engineering Department phone: 215-431-9349 (only by moonlite)
parker@zaphod.mpr.ca (Ross Parker) (03/20/90)
In article <10239@cbmvax.commodore.com>, grr@cbmvax.commodore.com (George Robbins) writes: > In article <384@vela.acs.oakland.edu> schemers@vela.acs.oakland.edu (Roland Schemers III) writes: > > Hello! I have a question about using 'dump'. How dangerious is it to > > dump an active file system? That is, dumping a file system that is > > mounted, and while the system is in multi-user mode? I have gotten > > various replies from DEC, ranging from "It might corrupt the whole dump", > > or "Only the active files will be messed up". > There's no really good answer to this question. If you want dump that > are guarenteed to be restorable without hassle, do *all* of the either > standalone or with the filesystem unmounted. > > Many sites compromise by doing the critical (level 0, weekly) dumps in > standalone mode and doing the daily incrementals while the system is up, > ideally during a low activity time period. > To put my $0.02 in, we perform weekly full and daily incremental backups *always in multi-user mode* on 33 *IX systems at MPR. We have been doing so for at least the 5 years that I've been here, and have *never* had an occasion where something has been lost. At least, we've never been caught missing a file - I'm sure our tapes have irretrievable 'holes' in them... CAVEAT - Because of the nature of dump, I know that we've been *extremely* lucky in this respect. If I could afford to take my systems down, I would do all of my dumps single-user. We currently do our dumps starting around 5:00 pm, when the building is starting to get quiet. Our full dumps are to 8mm tape, and are thus very fast, so the file systems don't change much during the dump. If you can afford to do it (I can't), it would be wise to dump in single user mode. Tar is *not* a good alternative, as it's tape error handling is nonexistant, and it will not handle every eventuality that a Berkeley file system can throw at it. Ross Parker parker@mpre.mpr.ca (604)293-5495 uunet!ubc-cs!mpre!parker
emv@math.lsa.umich.edu (Edward Vielmetti) (03/21/90)
My understanding is that the Ultrix ``dump'' has had some of the
Purdue modifications into it to harden it against problems with
dumping live filesystems. This information courtesy of Rich Kulawiec,
partial author of some of the Purdue changes, who says he's using the
supplied dump on the DS3100.
Here's a worst case test for dump, courtesy of
Don Speck <mangler@csvax.caltech.edu>:
mkdir foo; cd foo; sleep 999999 & cd ..; rmdir foo
dump that filesystem
restore that filesystem someplace (e.g. /usr/tmp)
see if restore dumps core on this one.
--Ed