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 > > ______________________________**_________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/**mailman/listinfo/zfs-discuss<http://mail.opensolaris.org/mailman/listinfo/zfs-discuss> > 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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