Question about dumps on Suns

[Dieter Muller]

In article <18506 at bellcore.bellcore.com> tr at bellcore.com (tom reingold) writes:
>
>On the subject of "Question about dumps on Suns",
>todd at lectroid.sw.stratus.com (Todd Joseph) writes:
>
>$ I'm performing dumps on a Sun server with an Exabyte 8mm backup system.  
>$ Dumping to an Exabyte takes a long time.  Consequently, performing dumps in 
>$ single-user mode takes the server out of use for a long time.  Does anyone 
>$ have experience with performing dumps in multi-user mode?
>
>It's not "supposed" to be a good thing, since you can lose some files
>while you back them up, but it's the only way I do backups, and I
>haven't had a disproportionate number of problems resulting from it.
>That is to say that the benefit of not taking the system down seems to
>outweigh the inconvenience of the occasional lost file.

Which is great until restore(8) decides the dump is corrupted and
refuses to have anything more to do with it.  We've had that happen
a couple of times.

Here's what I sent to Todd via e-mail, it may be of more general interest:

========================begin included message========================

Don't do it unless you've added the live filesystem mods from Purdue
to your dump.  You run a chance of restore not being able to read the
tape, the odds being directly proportional to filesystem activity at
the time of the dump .  This is true even for level 9 dumps, but is
particularly painful for the level 0 ones.

Unfortunately, this *does* require source for dump.  If you have 4.2
or 4.3 BSD source, that version of dump will work just fine.

The mods, btw, skip any files that change while dump is running.  This
translates to some files not getting dumped.  Two solutions:  A) tell
people that things changed between times X and Y aren't guaranteed
recoverable, or B) do a level 9 immediately after the level 0 completes.

=========================end included message=========================

We've made this change internally, and have had occassion to restore
from these dumps.  You get complaints about missing files, but the
entire tape set does get processed.

	Dworkin
--
sophisticate: to alter deceptively; esp. ADULTERATE --Webster's 7th Collegiate
boulder!stan!dworkin  dworkin%stan at boulder.colorado.edu  dworkin at solbourne.com
Flamer's Hotline: (303) 678-4624 (1000 - 1800 Mountain Time)