Zfs heavy io writing | zfskern txg_thread_enter

[Michelle Sullivan]

Don Lewis wrote:
> On 19 Feb, Niccolò Corvini wrote:
>   
>> Hi, first time here!
>> We are having a problem with a server running FreeBsd 9.1 with ZFS on a
>> single sata drive. Since a few days ago, in the morning the system becomes
>> really slow due of a really heavy io writing. We investigated and we think
>> it might start at night, maybe correlated to to crondaily (standard) but we
>> are not sure.  After a few hours the situation returns to normal.
>> Any help is much appreciated
>> The machine is a Intel Xeon E5-2620 with 36GB of RAM, the HDD is a 2TB an
>> is half full.
>>     
>
> The only way that you should get a lot of write traffic during the daily
> periodic runs is if atime updates are enabled.  I don't know what the
> default was for FreeBSD 9.1, but recent versions of FreeBSD disable
> atime updates on ZFS everywhere except /var/mail.  What does
> 	zfs get -o all atime
> say?
>   

On 9.2 and 9.3 it seems the default is (respectively):

NAME     PROPERTY  VALUE  RECEIVED  SOURCE
storage  atime     on     -         default

NAME                                 PROPERTY  VALUE  RECEIVED  SOURCE
VirtualDisks                         atime     on     -         default
VirtualDisks/FreeBSD10.0amd64-Build  atime     -      -         -
VirtualDisks/FreeBSD10.0amd64-OS     atime     -      -         -
VirtualDisks/FreeBSD10.1amd64-Build  atime     -      -         -
VirtualDisks/FreeBSD10.1amd64-OS     atime     -      -         -
VirtualDisks/FreeBSD8.4-Build        atime     -      -         -
VirtualDisks/FreeBSD8.4-OS           atime     -      -         -
VirtualDisks/FreeBSD9.0-Build        atime     -      -         -
VirtualDisks/FreeBSD9.0-OS           atime     -      -         -
VirtualDisks/FreeBSD9.1-Build        atime     -      -         -
VirtualDisks/FreeBSD9.1-OS           atime     -      -         -
VirtualDisks/FreeBSD9.2amd64-Build   atime     -      -         -
VirtualDisks/FreeBSD9.2amd64-OS      atime     -      -         -
VirtualDisks/FreeBSD9.2i386-Build    atime     -      -         -
VirtualDisks/FreeBSD9.2i386-OS       atime     -      -         -
VirtualDisks/FreeBSD9.3amd64-Build   atime     -      -         -
VirtualDisks/FreeBSD9.3amd64-OS      atime     -      -         -
VirtualDisks/FreeBSD9.3i386-Build    atime     -      -         -
VirtualDisks/FreeBSD9.3i386-OS       atime     -      -         -
sorbs                                atime     on     -         default
sorbs/VirtualDisks                   atime     -      -         -


It's probably the same for Niccolò on the 9.1 system.

Best regards,

Michelle

-- 
Michelle Sullivan
http://www.mhix.org/