Snapshot ufs blocking

[Kris Kennaway]

On Tue, Mar 14, 2006 at 09:30:27AM -0600, Eric Anderson wrote:
> Robert Watson wrote:
> >
> >On Sun, 12 Mar 2006, Eric Anderson wrote:
> >
> >>>Thanks.  There is an uncommitted patch being circulated that is 
> >>>believed to address all remaining problems.  It relies on other 
> >>>fixes in -CURRENT that are not yet merged, but if you're able to 
> >>>test it let me know and I'll forward.
> >>
> >>I can definitely test it - I'm running 6-STABLE currently, but I 
> >>suppose I could get -CURRENT on there for the testing..
> >
> >FYI, Jeff Roberson just did a large scale merge of 
> >UFS/VFS/snapshot/... bug fixes from HEAD to RELENG_6, see my HEADS UP 
> >post on -stable a day or so ago. It would be very useful to know if 
> >these help, and if not, you may want to drop e-mail to Jeff Roberson 
> >with a detailed description, since he's actively working on tracking 
> >down and fixing these issues.
> >
> >Robert N M Watson
> 
> Well, updating to the latest RELENG_6, I see that progress is definitely 
> being made.  I don't seem to be deadlocked anymore.  Commands like ls 
> and such work fine, until I ls the snapshot file itself, which blocked 
> for about 10 minutes before finally completing, and once that command 
> blocked (ufs) other ls -al commands blocked (ufs) on the root (/) 
> directory and subsequent subdirs down to the snapshot.  A 'sync' also 
> blocked during this time (blkrd?), but the difference this time is that 
> they all completed.  The snapshot completed within about 22 minutes (2Tb 
> filesystem, very little on this one), and commands returned before the 
> snapshot finished at about the 10 minute mark, and subsequent commands 
> (again, ls -al, etc), completed when the snapshot completed.  The 
> machine in question is a dual Xeon 2.8GHz with 4Gb of memory, running 
> SMP kernel (pretty much GENERIC), and was about 30% busy (cpu) mostly 
> 'system' and 'io'.  The disk being snapshotted was very busy though..

Yes, that's expected behaviour.

Kris
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