On 15 August 2011 15:55, Andrew Gabriel andrew.gabr...@oracle.com wrote:
David Wragg wrote:
I've not done anything different this time from when I created the
original (512b) pool. How would I check ashift?
For a zpool called export...
# zdb export | grep ashift
ashift: 12
^C
#
As far as I know (although I don't have any WD's), all the current 4k
sectorsize hard drives claim to be 512b sectorsize, so if you didn't do
anything special, you'll probably have ashift=9.
I would look at a zpool iostat -v to see what the IOPS rate is (you may
have bottomed out on that), and I would also work out average transfer size
(although that alone doesn't necessarily tell you much - a dtrace quantize
aggregation would be better). Also check service times on the disks (iostat)
to see if there's one which is significantly worse and might be going bad.
--
Andrew Gabriel
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from what i have read you really do need to 4k align your drives and
ashift=12 them on the western digitals. Unfortunately that probably means
you have to rebuild your pool. 4k aligining is fairly easy it just means
when you partition a disk, just make sure the 1st sector and the size of
the partition is /8. Ie dont start the 1st partition at sector 34 as
normally happens, start it at say 40. eg here are my 4k alinged drives from
a freebsd system
# gpart show ada0
=34 3907029101 ada0 GPT (1.8T)
34 6- free - (3.0k)
40 128 1 freebsd-boot (64k)
168 6291456 2 freebsd-swap (3.0G)
6291624 3900213229 3 freebsd-zfs (1.8T)
making ashift=12 is a little more tricky. I have seen a patch posted on the
mailing lists for zpool which forces it. Alternatively you could boot into a
freebsd live cd and create the pool with the 'gnop -S 4096' trick. Its
possible there is another way to do it now on opensolaris that i havent
come across yet
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