zfs on 4k sector disks

[Marty Rosenberg]

I've tried running zfs on a maximum of 22 disks in various configurations
with
raidz and raidz2, and 4-7 devices in each vdev.  In general, the performance
has
been pretty abysmal.  Using gnop to emulate a disk with 4k sectors, the
performance usually starts out in a reasonable place (60-100MB/s, about the
write speed of an individual disk), but after adding 30 or so gigabytes of
data, the
write speed drops dramatically. down to 1-3 MB/s in most instances.


On Sat, Jul 3, 2010 at 7:44 PM, Bucarr <bucarr at gmail.com> wrote:

>
>
>
> On Sat, 3 Jul 2010 11:28:03 -0700 (PDT)
> Bucarr <bucarr at gmail.com> wrote:
>
> > I was wondering that as well.  So I set up a new FreeBSD8.0 box with
> > a UFS2 disk as my boot disk and two WD 2TB EARS drives ("Advanced
> > Format") for a zfs data array.  I made no attempt to alter the WD
> > drives in any way and ignored the 512b vs 4096b issues.  'zpool
> > create tank raidz da0 da1' set up the array in a few seconds and I've
> > copied to/from with no troubles and no apparent performance issues
> > that I care about.  If I had more of the WD drives lying around, I'd
> > add those to the array and see what gives then.
>
> I suspect the performance may be acceptable, but probably not great.
> I thought I didn't have any problems with RAIDZ's variable stripe size
> on my EARS drives either until I found some writes would suddenly take
> ages to finish, causing applications to hang.
>
> --
> Bruce Cran
>
>
> I wonder if my 2 drive experiment in RAIDZ didn't simply mirror the drives
> so that striping wasn't invoked at all?
> --
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