Zfs locking up process

[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?
> So you cannot "share" the dataset between to jails without the risk of
> hangs - its a problem inside the VFS.
>
> You should set the mountpoint via "zfs set" inside your jail. But you
> can do this only for one jail.
>
> Regards
> Michael
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