[PC-BSD Testing] Panic from ZFS

Kris Moore kris at pcbsd.com
Fri Oct 24 07:23:30 PDT 2008

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 

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

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