Re: [Testperf-general] dbt2 & opteron performance

On Thu, 28 Jul 2005 16:55:55 -0700
Mark Wong <markw(at)osdl(dot)org> wrote:

> On Thu, 28 Jul 2005 18:48:09 -0500
> "Jim C. Nasby" <decibel(at)decibel(dot)org> wrote:
>
> > On Thu, Jul 28, 2005 at 04:15:31PM -0700, Mark Wong wrote:
> > > On Thu, 28 Jul 2005 17:17:25 -0500
> > > "Jim C. Nasby" <decibel(at)decibel(dot)org> wrote:
> > >
> > > > On Wed, Jul 27, 2005 at 07:32:34PM -0700, Josh Berkus wrote:
> > > > > > This 4-way has 8GB of memory and four Adaptec 2200s controllers attached
> > > > > > to 80 spindles (eight 10-disk arrays). For those familiar with the
> > > > > > schema, here is a visual of the disk layout:
> > > > > > http://www.osdl.org/projects/dbt2dev/results/dev4-015/layout-6.html
> > > >
> > > > Have you by-chance tried it with the logs and data just going to
> > > > seperate RAID10s? I'm wondering if a large RAID10 would do a better job
> > > > of spreading the load than segmenting things to specific drives.
> > >
> > > No, haven't tried that. That would reduce my number of spindles as I
> > > scale up. ;) I have the disks attached as JBODs and use LVM2 to stripe
> > > the disks together.
> >
> > I'm confused... why would it reduce the number of spindles? Is
> > everything just striped right now? You could always s/RAID10/RAID0/.
>
> RAID10 requires a minimum of 4 devices per LUN, I think. At least 2
> devices in a mirror, at least 2 mirrored devices to stripe.
>
> RAID0 wouldn't be any different than what I have now, except if I use
> hardware RAID I can't stripe across controllers. That's treating LVM2
> striping equal to software RAID0 of course.

Oops, spindles was the wrong word to describe what I was losing. But I
wouldn't be able to spread the reads/writes across as many spindles if I
have any mirroring.

Mark