Snapshot ufs blocking

[Eric Anderson]

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..


Eric




-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.
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