New ZFSv28 patchset for 8-STABLE

[J. Hellenthal]

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On 01/01/2011 13:18, Attila Nagy wrote:
>  On 12/16/2010 01:44 PM, Martin Matuska wrote:
>> Link to the patch:
>>
>> http://people.freebsd.org/~mm/patches/zfs/v28/stable-8-zfsv28-20101215.patch.xz
>>
>>
>>
> I've used this:
> http://people.freebsd.org/~mm/patches/zfs/v28/stable-8-zfsv28-20101223-nopython.patch.xz
> 
> on a server with amd64, 8 G RAM, acting as a file server on
> ftp/http/rsync, the content being read only mounted with nullfs in
> jails, and the daemons use sendfile (ftp and http).
> 
> The effects can be seen here:
> http://people.fsn.hu/~bra/freebsd/20110101-zfsv28-fbsd/
> the exact moment of the switch can be seen on zfs_mem-week.png, where
> the L2 ARC has been discarded.
> 
> What I see:
> - increased CPU load
> - decreased L2 ARC hit rate, decreased SSD (ad[46]), therefore increased
> hard disk load (IOPS graph)
> 
> Maybe I could accept the higher system load as normal, because there
> were a lot of things changed between v15 and v28 (but I was hoping if I
> use the same feature set, it will require less CPU), but dropping the
> L2ARC hit rate so radically seems to be a major issue somewhere.
> As you can see from the memory stats, I have enough kernel memory to
> hold the L2 headers, so the L2 devices got filled up to their maximum
> capacity.
> 
> Any ideas on what could cause these? I haven't upgraded the pool version
> and nothing was changed in the pool or in the file system.
> 

Running arc_summary.pl[1] -p4 should print a summary about your l2arc
and you should also notice in that section that there is a high number
of "SPA Mismatch" mine usually grew to around 172k before I would notice
a crash and I could reliably trigger this while in scrub.

What ever is causing this needs desperate attention!

I emailed mm@ privately off-list when I noticed this going on but have
not received any feedback as of yet.

[1] http://bit.ly/fdRiYT

- -- 

Regards,

 jhell,v
 JJH48-ARIN
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