XFS blocked task in xlog_cil_force_lsn

[Stefan Priebe - Profihost AG]

Am 17.04.2012 10:32, schrieb Dave Chinner:
>>> What's your storage hardware, application, workload, etc?
>> It a Raid 10 of 1TB SATA Drives in front of a 3Ware Controller doing
>> heavy rsync backups.
> 
> Hmmm. It sounds like it is just taking a long time for the IO to
> complete, not that there is any other problem. If the IO is realy,
> really slow, the a log force is definitely a place it coul dstall
> for some time.
OK as i've seen this just once it just might be that the controller /
disks were too slow in this case.

> Does the RAID controller have a BBWC?
No but doesn't matter ;-) If it crashes i can just repair the FS and
restart the backup again.

> What IO scheduler are you using?
[root at backup1 ~]# cat /sys/block/sdc/queue/scheduler
[noop] deadline cfq

> Does mounting with nobarriers reduce the stall time?
It is already mounted with nobarrier:
/dev/sdc3 on /sdc3 type xfs (rw,noatime,nodiratime,nobarrier,prjquota)

> Can you reduce the IO load so that it doesn't end up in this state?
Can try that by just doing less backups per time period.

Stefan