Hello Jeff,
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.
Thanks,
Herbert.
On 10/25/2012 06:32 PM, Jeff Paterson wrote:
Hello,
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.
The "hanging pattern" is easily reproductible. If I write a 1GB file
on the filesystem, it does the following:
- write ~200 MB of data on the disk in 1 second
- freeze for about 10 seconds
- write ~200 MB of data on the disk in 1 second
- freeze for about 10 seconds
- write ~200 MB of data on the disk in 1 second
- freeze for about 10 seconds
(and so on)
When the freezes occur:
- other writes operations (from other processes) on the same
node also freeze
- writes operations on other nodes are not affected by the
freezes on another node
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 don't cause the filesystem freeze.
For info, before the problem began to appear we could sustain 640 MB/s
writes without any freeze.
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.
*_Filesystem details_*
* The filesystem has 18 TB and it is currently 72% full.
* Mount options are the following:
rw,nodev,_netdev,noatime,errors=panic,data=writeback,noacl,nouser_xattr,commit=60,heartbeat=local
* All Features: backup-super strict-journal-super sparse
extended-slotmap inline-data metaecc indexed-dirs refcount
discontig-bg unwritten
There is nothing special in the systems logs beside application errors
caused by the freezes.
Would a fsck.ocfs2 help? How long would it take for 18 TB?
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?
Any help would be greatly appreciated.
Thanks in advance,
Jeff
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