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Date:      Sun, 11 Oct 2015 15:37:18 +0200
From:      Michael Ranner <michael@ranner.eu>
To:        Steven Hartland <killing@multiplay.co.uk>, freebsd-fs@freebsd.org
Subject:   Re: Zfs locking up process
Message-ID:  <561A660E.1020905@ranner.eu>
In-Reply-To: <561A5445.40603@multiplay.co.uk>
References:  <CAFoaQoDdKHzASfgxY7ptHuqk=nCsxvpq4q3gr9_QsUK4Hkim9w@mail.gmail.com> <CAFoaQoCB5CmorF4wfabz7iBaqxzxxggdqJiqePUTqLCnFichWA@mail.gmail.com> <CAFoaQoAt--8pGh_vGVTfVWjEBJ5uRM0Tr6TS-czFbQ-eSHKvXg@mail.gmail.com> <CAFoaQoDVt5eJKTjcmGmR2fmQoL_WQV1ZebNUb_K9qLY4=cOi6A@mail.gmail.com> <561A2A4B.4080704@ranner.eu> <561A5445.40603@multiplay.co.uk>

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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



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