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Re: Software RAID blocks




Hi!


On Sun, Jan 13, 2019 at 12:27:19PM +0100, Tom Bachreier wrote:
> Last night I got a "blocked for more than 300 seconds." message in syslog -
> see <https://paste.debian.net/1060134/ <https://paste.debian.net/1060134/>> (link valid for 90 days).
> 
> Log summary:
> Jan 13 02:34:44 osprey kernel: [969696.242745] INFO: task md127_raid5:238 blocked for more than 300 seconds.
> Jan 13 02:34:44 osprey kernel: [969696.242772] Call Trace:
> Jan 13 02:34:44 osprey kernel: [969696.242789]  ? __schedule+0x2a2/0x870
> Jan 13 02:34:44 osprey kernel: [969696.242995] INFO: task dmcrypt_write:904 blocked for more than 300 seconds.
> Jan 13 02:34:44 osprey kernel: [969696.243223] INFO: task jbd2/dm-2-8:917 blocked for more than 300 seconds.
> Jan 13 02:34:44 osprey kernel: [969696.243525] INFO: task mpc:6622 blocked for more than 300 seconds.
> Jan 13 02:34:44 osprey kernel: [969696.243997] INFO: task kworker/u8:0:6625 blocked for more than 300 seconds.

I am occasionally having very similar issues with my RAID1, task
blocking for more than 120 seconds, for no obvious reason.

I've started playing around with the vm.dirty_background_ratio and
vm.dirty_ratio kernel parameters, suspecting file system caching being
slow and the issue. [1]

While lowering the values does seem to have helped, it has not
completely eliminated the issue. So the jury for me is still out.

> In this case I did a
>   $ fdisk -l /dev/sdf
> and everything worked again.

Not sure if/how this would interact with ongoing cache flushing.

	Jens


[1] https://www.blackmoreops.com/2014/09/22/linux-kernel-panic-issue-fix-hung_task_timeout_secs-blocked-120-seconds-problem/