Snapshot usage guidelines (to avoid stability issues)

[Kostik Belousov]

On Thu, Jun 21, 2007 at 01:45:32AM +0300, Cristian KLEIN wrote:
> Kostik Belousov wrote:
> > On Wed, Jun 20, 2007 at 06:26:26PM +0200, Espen Skoglund wrote:
> >> Hi,
> >>
> >> A couple of days ago I decided to start using snapshots on my system.
> >> Knowing that the functionality has been available for quite some time
> >> now I (apparently wrongly) assumed that it was ready for production
> >> use.  My bad.
> >>
> >> My system, a 6-STABLE from week and a half ago, uses two 250GB
> >> gstriped disks and has about 4-5 snapshots on one 215GB UFS partiton.
> >> This morning I learned that things had gone terribly wrong during some
> >> nightly cronjobs, hanging the whole system.  Suspecting that snapshots
> >> were the culprit I soon learned after some investigation that the
> >> snapshot functionality wasn't nearly as stable as I had hoped for.
> >>
> >> Looking at PRs and mailing lists there seems to be mainly two
> >> outstanding stability issues with snapshots: a) snapshotted fs running
> >> full, and b) deleting large amount of files on an fs with multiple
> >> snapshots.  The former issue, while certainly annoying, one could be
> >> able to work around.  The latter issue, on the other hand, seems more
> >> like a definite show stopper.
> >>
> >> Am I right in inferring that the two above cases are main issues with
> >> snaphots at this time, or are there other known gotchas that I have to
> >> look out for.
> > About the issue b). Are you system sources before or after 2007-06-11
> > 10:53:48 UTC ? Or simply show me the version of sys/ufs/ffs/ffs_snapshot.c.
> > 
> > If it is less then 1.103.2.24, see developers handbook for instruction on
> > reporting deadlocks.
> > 
> 
> Do you think that 1.103.2.24 might solve this
> http://lists.freebsd.org/pipermail/freebsd-fs/2007-May/003161.html ?
I very much doubt it. AFAIR, I asked at least ddb backtrace for the crash,
and you did not answered.
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