Re: raid 10 su, sw settings

[Brad Langhorst <brad@langhorst.com>]

On Mon, 2007-12-31 at 21:17 +0100, Iustin Pop wrote:
> On Mon, Dec 31, 2007 at 02:07:27PM -0500, Justin Piszcz wrote:
> > On Mon, 31 Dec 2007, Brad Langhorst wrote:
> >> On Mon, 2007-12-31 at 12:04 -0500, Justin Piszcz wrote:
> >>
> >>>>
> >>>> Typical blocks/sec from iostat during large file movements is about
> >>>> 100M/s read and 80M/s write.
> >>>>
> >>>
> >>> #1 What type of performance do you expect with a 4-disk raid10?
> >>
> >> Are you saying that i should not expect more?
> >> I expect about 70% better performance, since I think a single disk
> >> should be able to do 100M/s. Maybe this is unreasonable?
> > A single disk may do 90MiB/s burst but not sustained for read or write, at 
> > least not cheap SATA disks and when you get toward the middle part of the 
> > disk the speed wil drop off significantly.  100MiB/s read and 80MiB/s write 
> > for RAID10 sounds about right to me.  Maybe someone else on the list with a 
> > similar configuration can chime in with their benchmarks.
> 
> I agree about the disk speed - 100MiB/s for SATA drives is a little bit
> too much to expect. And certainly, *only* in purely single-reader or
> single-writer sequential workloads.
> 
> I have the same config - 4 drive hw raid10 on 9650. A recent zcav log
> shows read speeds start at around 140MiB/s and decrease toward 75MiB/s.
> Since this is zcav from the bonie++ package, it doesn't take into
> account any filesystem or partitioning overhead.

I guess I should re-adjust my expectations

Any opinions on the partition layout? Did you go to special effort to
layout your partitions on the stripe boundaries (actually i don't really
understand this fully yet).