Swap on ZFS Volume still panics?

[jhell]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 09/10/2010 03:39, Pawel Jakub Dawidek wrote:
> On Wed, Sep 08, 2010 at 07:19:40PM +0300, App Deb wrote:
>> Reading the wiki guides they mention the official way to add swap volumes on
>> ZFS (set org.freebsd:swap=on etc..),
>>
>> So I thought that it should work now, But I just got a panic in 8.1-RELEASE
>> after a heavy memory situation that touched swap for the first time.
> 
> Swap on ZVOL is still not recommended. Where did you find information
> that it now recommended? I can't find anything about swap on
> http://wiki.freebsd.org/ZFS and on
> http://wiki.freebsd.org/ZFSQuickStartGuide there is a note that it is
> not recommended. Let me know where it is advised and I'll remove it or
> add a note (if the documentation is mine).
> 
>> It is a hassle to add gmirror volumes for swap on full zfs systems, is there
>> any workaround for this, or any news when a fix is coming or if it is
>> coming?
> 
> I've no plans to fix it, maybe with ZFSv28 it will be easier to fix, but
> this is really low priority. If you use full ZFS system the recommended
> layout is described here:
> 
> 	http://blogs.freebsdish.org/pjd/2010/08/06/from-sysinstall-to-zfs-only-configuration/
> 
>> If the current code procudes guaranteed panics with zfs swap, I think that
>> every mention of swap on zfs should be removed from the semi-official wiki
>> guides.
> 
> BTW. If this issue will be worked on in the future, it will be useful to
> actually see your panic, backtrace and other debug info. To be honest, I
> didn't expect it to panic, rather deadlock. Maybe panic is from deadlock
> resolver? Hard to say without any debug info.
> 

For reference I have been using swap on ZFS for a while. I recieve no
panics when doing so and have the following properties set.

exports/swap  refreservation        2G                     local
exports/swap  primarycache          none                   local
exports/swap  secondarycache        none                   local
exports/swap  org.freebsd:swap      on                     local

As someone already mentioned, it might help to also change volblocksize
property to 4k but I have never had to do that as changing the primary
and secondary caches were enough to keep it from panic here.

I would be interested to hear if this helped anyone else.


Regards,

- -- 

 jhell,v
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.16 (FreeBSD)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

iQEcBAEBAgAGBQJMiypWAAoJEJBXh4mJ2FR+OeYH/0jxC6aJlOHVKxL8UCeA+94s
V3scx8jDH3ZiqoCno4FLgkzW41E1NUGlvZA4arLe76Fv2/QeU53ZyZD160WcRYax
fhOyUQeHPJ2QecSnsmBJS2aJSvl9abdNYMyEhA1YxoApvBRcm7FEvAt3qY8Dj5uQ
jJPN4zOxM6CGq6FUWEbAmmtpIKSi/TLNZqvpxN1GcJeyfyFJroswiEisWYq2rkEA
MqXEe13DqVdjS0yysyMHsGNqfgpByDRQJ4M/nnGMPHyUlGdItFJR2B3htzVdeb88
69TnEw5rwiztNm/629jyBaDdynjwortP3Jw37Mij6SE/kHS/+kZ6dfCb7eZHPmA=
=PAEM
-----END PGP SIGNATURE-----