HEADS UP: New ZFS in the tree.

Thomas Vogt thomas at bsdunix.ch
Thu Dec 4 15:58:22 PST 2008

Wes Morgan schrieb:
> On Thu, 4 Dec 2008, Thomas Vogt wrote:
>> Hello Stefan
>> Am 04.12.2008 um 00:33 schrieb Stefan Bethke:
>>> Am 03.12.2008 um 00:29 schrieb Peter Schuller:
>>>>> I've noticed the past couple of days, when using the server (not very
>>>>> often), every now and then, the GUI (KDE 4.1) will "hang" for up to 5
>>>>> minutes (no mouse movement, no keyboard events), while the drives 
>>>>> work like
>>>>> crazy.
>>>> I was not explicit about it, but FWIW in my case the hang is not due
>>>> to drive saturation. The drives were mostly idle (except some stuff
>>>> triggered by a buildworld I had going) during the extended period of
>>>> ktorrent being unkillable. But again I never had this happen
>>>> pre-CURRENT.
>>> Just a very brief "me too" (but possibly different effect): I'm 
>>> stress testing two machines I put together over the weekend with an 
>>> endless loop of make -j4 universe, with /usr/obj on ZFS, with a 
>>> single disk. One of the two machines has now been stuck for a couple 
>>> of hours, and trying to access /tank results in a hung process, as 
>>> will zfs list.
>>> I'll reboot and see what happens, and if I can trigger it again, 
>>> willt try to produce more details.
>>> I have set
>>> vfs.zfs.arc_max="512M"
>>> vfs.zfs.prefetch_disable=1
>>> in loader.conf
>>> FreeBSD lokschuppen.lassitu.de 8.0-CURRENT FreeBSD 8.0-CURRENT #1: 
>>> Wed Dec 3 07:05:03 UTC 2008 
>>> root at lokschuppen.lassitu.de:/usr/obj/usr/src/sys/EISENBOOT  amd64
>> Try to disable ZIL in loader.conf:
>> vfs.zfs.zil_disable="1"
>> It helped me to stop deadlocks during rsync processes. As long as you 
>> don't run any databases or any fsync() intensiv applications,  i don't 
>> see any drawbacks in disabling zil. The drawbacks are for the 
>> applications itself not for ZFS. ZFS will be always consistent on disk 
>> due to its transaction model even without ZIL.
> Are you sure about that? Without the ZIL, wouldn't you need to scrub 
> each pool after every crash, much as fsck with UFS?

AFAIK no. 
The ZFS pool integrity itself is not compromised by this tuning.

There are many blog entries from ZFS developer with the same conclusion.


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