[PC-BSD Testing] Panic from ZFS

Edward O'Callaghan victoredwardocallaghan at gmail.com
Fri Oct 24 08:07:38 PDT 2008

Actually Kris,

My point was that you could suffer complete data corruption !
I know about the message as I asked for it to be put there, remember ;)

I really do think it should be disabled on systems where it should not
be running on until you are using FreeBSD 8 with the update to version
11. That is, that I can now confirm that it does indeed resolve the
memory issue.


2008/10/25 Kris Moore <kris at pcbsd.com>:
> Arthur wrote:
>> At 02:49 AM 10/24/2008, you wrote:
>>> On Fri, Oct 24, 2008 at 7:30 AM, Edward O'Callaghan
>>> <victoredwardocallaghan at gmail.com> wrote:
>>>> Hi,
>>>> You can get version 6 of zfs to panic in FreeBSD by doing the following;
>>>> * Have 512 or less MB of RAM
>>>> * Fill most of your zpool up then run a zpool scrub on the pool..
>>>> This is a out-of-memory kernel panic that particularly affects i386.
>>>> My suggested work around is to put the following into loader.conf
>>>> vfs.zfs.zil_disable=1
>>>> vfs.zfs.prefetch_disable=1
>>>> N.B. Disabling ZIL can have serious consequences depending on
>>> your workload.
>>>> FreeBSD 8 upgrades ZFS to version 11. However I am not sure how this
>>>> affects things as this only happens on FreeBSD and not Solaris.
>>>> Kris, As I said before. I highly recommend you disable ZFS support on
>>>> 32bit systems with less then 1gb of ram else people _could_ lose data
>>>> ?
>>> I've always believed that there is a HEADS UP somewhere that said
>>> something about dedicating at least 1GB for ZFS on FreeBSD.
>> Yes, I remember this as well.
>> Arthur
> Correct! If you try to install with ZFS, this message appears first, and
> you have to click "OK" to continue:
> "Warning: ZFS usage is primarily for high-end systems with a 64 bit
> processor and 4+ GB of memory. It may run on lesser hardware, but is not
> recommended."
> That pretty much covers all the bases here. I don't want to outright
> disable ZFS, since some users have enjoyed testing / playing with it on
> systems with 512MB of ram in qemu / vmware or on a test desktop. Its
> more of a learning experience for them to just play with zfs and see how
> it works. (I've done that myself a bit, on some of my older systems)
> However, again, the message does let users know that it should have 4GB
> of memory, and use the amd64 release if possible.
> --
> Kris Moore
> PC-BSD Software
> http://www.pcbsd.com
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> Testing at lists.pcbsd.org
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