zfs mirror reads only on one disk

[Jeremie Le Hen]

On Tue, Aug 09, 2011 at 06:52:12AM -0700, Jeremy Chadwick wrote:
> 
> Performance was a little less than I estimated (I really don't care to
> be honest), but this double-confirms that yes, reads do get split across
> mirror members.

By the way, I tried with the same disk (WD Caviar Black) (not the same
size though) on Solaris 11:

                    extended device statistics
    r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device
 1104.5    0.0 141371.6    0.0  0.0  0.9    0.0    0.9   1  95 c5t5d0
                    extended device statistics
    r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device
 1101.7    0.0 141014.0    0.0  0.0  0.9    0.0    0.9   1  95 c5t5d0

It can reach 140 MB/s!

> Therefore I cannot explain what you're seeing.  Maybe consider upgrading
> to a newer RELENG_8 and ZFSv28 and see if things improve?  I wish I had
> a way to confirm this would fix your problem but I do not.

Ok, I didn't know ZFS v28 was MFC'd to RELENG_8.  By the way, I see you
switched to the new ata(4) driver according to your device names.  Is it
painless to upgrade?  I'll give it a try this evening hopefully.

Thanks.
Regards,
-- 
Jeremie Le Hen

Humans are born free and equal.  But some are more equal than others.
					    Coluche