UFS2 Snapshots in 6.1-Beta4 - Confirmed Problems.

[Julien Gabel]

> While we're on the topic of snapshots, I recently posted this follow-up to
> the PR kern/66270 "[hang] dump causes machine freeze"

>> I wonder what is the status of this PR?
>>  I seem to have the same problem with 5.3-RELEASE.
>>
>>  Before this started, system worked nicely for more than a year and then
>> it
>>  started to hang during dump (seemingly just after mksnap_ffs) first
>>  intermittently and now reproducibly (might increase in data size be a
>>  factor? though disk is only about 18% full).
>>  Originally it hanged and console had complains about increasing
>>  PMAP_SHPGPERPROC and maxproc.
>>  After some talk in freebsd-fs, I adjusted these parameters and now it
>> just hangs without complaining =((
>>
>>  Any suggestions?

> In addition to this PR, I found a couple of similar threads in different
> lists but they all just have some initial talk and preliminary analysis,
> and then it just stops. Was that snapshot problem fixed or is it the same
> as we are talking now? I can't believe I am the only one in almost 2
> years who is (trying to be) doing automated backups...
> So, if it was fixed, when (which version)? If not, then when it might be
> and -- in the meantime -- is there any workaround for backups? (The system
> is the production server on the colocation so doing backups in single-user
> mode is not practical).

Interesting.  I used dump/restore without problem on i386 using a file
system of 120Go.  I swiched two weeks ago on amd64 using a file system of
260Go and encountered the very same behaviour (hang, freeze).  Don't know
if it is related to the new processor architecture or the bigger fs size,
but i didn't observe this hang on smallest file system before.

Because i am a big fan of dump, i currently choose to use it without the
'-L' switch, back to the old (classical?) behaviour, i.e. not doing a
snapshot before doing the dump.  It is always better than not having
complete system backup at all (YMMV, though).

I am currently running 6.1-PRERELEASE build Wed Mar 22 03:55:42 CET 2006.

-- 
-jpeg.