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Hello Jeff,<br>
<br>
You might want to check what the writer process is waiting on when
it's frozen. The wchan column of ps might be enough, but if not,
then perhaps a kernel stack trace of the process from
/proc/<pid>/stack or from echo t > /proc/sysrq-trigger .
The latter will show other blocked processes as well, which may be
helpful in determining the cause of the freeze.<br>
<br>
Thanks,<br>
Herbert.<br>
<br>
<br>
On 10/25/2012 06:32 PM, Jeff Paterson wrote:
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<font size="2"><span style="white-space: nowrap; color: rgb(34,
34, 34); font-family: arial, sans-serif;">Hello,</span><br>
</font>
<div>
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<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap"><br>
</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap">I would need help with our
OCFS2 (1.8.0) filesystem. We are having problems with
it since a couple days. When we write onto it, it
hangs.</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap"><br>
</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap">The "hanging pattern" is
easily reproductible. If I write a 1GB file on the
filesystem, it does the following:</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap"> - write ~200 MB of
data on the disk in 1 second</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap"> - freeze for about
10 seconds</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap"> - write ~200 MB of
data on the disk in 1 second</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap"> - freeze for about
10 seconds</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap"> - write ~200 MB of
data on the disk in 1 second</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap"> - freeze for about
10 seconds</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap"> (and so on)</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap"><br>
</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap">When the freezes occur:</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap"> - other writes
operations (from other processes) on the same node
also freeze</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap"> - writes operations
on other nodes are not affected by the freezes on
another node</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap"> </span></font></div>
<div><font size="2"><font color="#222222" face="arial,
sans-serif"><span style="white-space:nowrap">Read
operations (on any cluster node, even the one with
frozen writes) don't seem to be affected by the
freezes. One sure thing, read operations alone d</span></font><span
style="white-space:nowrap;color:rgb(34, 34,
34);font-family:arial, sans-serif">on't cause the
filesystem freeze.</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap"><br>
</span></font></div>
<div><font color="#222222" face="arial, sans-serif" size="2"><span
style="white-space:nowrap">
<div>For info, before the problem began to appear we
could sustain 640 MB/s writes without any freeze.</div>
<div><br>
</div>
<div>I tried to mount the filesystem on a single node
to avoid issues that could happen with inter-node
communications and the problem was still there.</div>
<div><br>
</div>
<div><br>
</div>
<div><b><u>Filesystem details</u></b></div>
<div>
<ul>
<li>The filesystem has 18 TB and it is currently
72% full.</li>
<li>Mount options are the following:
rw,nodev,_netdev,noatime,errors=panic,data=writeback,noacl,nouser_xattr,commit=60,heartbeat=local</li>
<li>All Features: backup-super
strict-journal-super sparse extended-slotmap
inline-data metaecc indexed-dirs refcount
discontig-bg unwritten</li>
</ul>
</div>
<div><br>
</div>
<div><br>
</div>
<div>There is nothing special in the systems logs
beside application errors caused by the freezes.</div>
<div><br>
</div>
<div><br>
</div>
<div>Would a fsck.ocfs2 help? How long would it take
for 18 TB?</div>
<div><br>
</div>
<div>Is there a flag I can enable in debugfs.ocfs2 to
get a better idea of what is happening and why it is
freezing like that?</div>
<div><br>
</div>
<div><br>
</div>
<div>Any help would be greatly appreciated.</div>
<div><br>
</div>
<div>Thanks in advance,</div>
<div><br>
</div>
<div>Jeff</div>
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