Zfs locking up process

[Michael Ranner]

Am 11.10.15 um 14:21 schrieb Steven Hartland:
>
>
> On 11/10/2015 10:22, Michael Ranner wrote:
>> Am 07.10.15 um 17:11 schrieb Rajil Saraswat:
>>> Hello
>>>
>>> I have server running Freenas 9.3 with a few jails. The machine has
>>> two new
>>> disks setup in mirror. I have a dataset (/mnt/tank/media) which is
>>> shared
>>> in two jails.
>>>
>>> Unfortunately, sometimes when I do a ls in a jail in the shared
>>> directory I
>>> see that the process just hangs.
>>>
>>> Today in the jail I did an 'su'  and process just hung. On the host
>>> if i do
>>> ls /mnt/tank/media it also hangs.
>>>
>>> The su process (pid 77477) is taking up 100% cpu in the jail. It
>>> seems that
>>> zfs is holding up the process. Any idea what could be wrong?
>>>
>>>
>> It is a known problem with ZFS and nullfs. I had no problems under
>> FreeBSD 8 witch such a setup, but since FreeBSD 9 it is very unstable to
>> mount_nullfs on ZFS. I experienced the same behaviour with Apache jails
>> and PHP, mostly PHP running with 100% CPU inside the jail.
> I'd have to disagree with this we have hundreds of machines on 10.1
> which uses nullfs every day and we've never seen a lockup.
>
> Given that do you have more information about this e.g. PR?
There are some posts to freebsd-fs in 2014 like this:

https://lists.freebsd.org/pipermail/freebsd-fs/2014-November/020482.html

And an in depth insight von Andriy Gapon:

https://lists.freebsd.org/pipermail/freebsd-fs/2014-September/020072.html

The problem will become more frequently with heavy snapshot usage on the
underlying ZFS datasets.

Regards
Michael