Re: zfs hang

----- Original Message ----- 
From: "Steve Wills" <swills_at_freebsd.org>
To: "Andriy Gapon" <avg_at_freebsd.org>
Cc: <current_at_freebsd.org>; <fs_at_freebsd.org>
Sent: Friday, October 10, 2014 2:27 AM
Subject: Re: zfs hang


> On Wed, Oct 08, 2014 at 08:55:26AM +0300, Andriy Gapon wrote:
>> On 08/10/2014 03:40, Steve Wills wrote:
>> > Hi,
>> > 
>> > Not sure which thread this belongs to, but I have a zfs hang on one of my boxes
>> > running r272152. Running procstat -kka looks like:
>> > 
>> > http://pastebin.com/szZZP8Tf
>> > 
>> > My zpool commands seem to be hung in spa_errlog_lock while others are hung in
>> > zfs_lookup. Suggestions?
>> 
>> There are several threads in zio_wait.  If this is their permanent state then
>> there is some problem with I/O somewhere below ZFS.
> 
> Thanks for the feedback. It seems one of my disks is dying, I rebooted and it
> came up OK, but today I got:
> 
>  panic: I/O to pool 'rpool' appears to be hung on vdev guid ..... at '/dev/ada0p3'
> 
> I have screenshots and backtrace if anyone is interested. Dying drives
> shouldn't cause panic, right?

Its the deadman timer kicking in so yes, thats expected.

The following sysctls control this behaviour if you want to try and recover:
vfs.zfs.deadman_synctime_ms: 1000000
vfs.zfs.deadman_checktime_ms: 5000
vfs.zfs.deadman_enabled: 1

    Regards
    Steve