Glenn is very much correct here. The application will dictate what
your upper limit will be. A highly sequential Oracle workload will
different greatly from a 5000 user exchange cluster.
That curve in raid groups is around 20 disks in my experience.
Eventually you'll run out of head room for the number of disks you've
attached.
-Blake
On 10/4/06, Glenn Walker <ggwalker(a)mindspring.com> wrote:
> There is a ceiling in performance gain after a certain number of disks
> it's well below 112, but I'm pretty sure it's above 56 (though not much
> above it). At that point, the 'curve' starts to go back down again.
>
> However, RAID-DP and RAID-4 (it's poor, homely cousin) are very fast and
> the filer has always handled the XORs very well for the parity
> calculations.
>
> A better question\way to position this might be what type of
> workload\performance you expect\require. While the disks are capable of
> about 120 IOPS for 10k and 180 IOPS for 15K disks, the latencies begin
> to jump at the end of the scale - if you're workload requires lower
> latencies, it doesn't much matter what the disk is capable of (Exchange
> is a very good example of this - 80 IOPS for 10k drives is about the max
> you'd want to go).
>
> Glenn
>
> -----Original Message-----
> From: owner-toasters(a)mathworks.com [mailto:owner-toasters@mathworks.com]
> On Behalf Of Suresh Rajagopalan
> Sent: Wednesday, October 04, 2006 3:56 PM
> Cc: toasters(a)mathworks.com
> Subject: RE: Estimating Aggregate IOPS
>
> Let's assume 4k IOPS. Disks are currently 10k rpm.
>
> Are you saying that NTAP's implementation of RAID4 (or RAID-DP) gives a
> linear performance increase with spindles, (almost like RAID-0) and no
> penalty for the RAID4 or RAID-DP?
>
> That is, aggregate IOPS is pretty much (N * disk-iops) and no penalty
> for RAID4 or RAID-DP?
>
> Thanks
> Suresh
>
>
>
> -----Original Message-----
> From: Blake Golliher [mailto:thelastman@gmail.com]
> Sent: Wednesday, October 04, 2006 12:41 PM
> To: Suresh Rajagopalan
> Cc: toasters(a)mathworks.com
> Subject: Re: Estimating Aggregate IOPS
>
> How fast are the spindles, and what size is your iop? Generally, you
> can assume 110 per 10k RPM disk, and 180 for 15k RPM disk. This is
> also assuming a 10ms latency for each iop. And subtract 2 disks per
> raid group for raid dp (if doing writes, don't if you are doing pure
> reads). So with around 50 disks (after you subtract the raid dp
> overhead) you can expect around 5500 iops from that set of disks
> (assuming 10k rpm disks). For the 112 aggregate, you an expect 98
> spindles
> and 10780 iops. I'm assuming 4k iops, and 10ms latency.
>
> Hope that helps,
> -Blake
>
>
> On 10/4/06, Suresh Rajagopalan <SRajagopalan(a)williamoneil.com> wrote:
> > Given a disk IOPS of 100, I'd like to estimate total aggregate IOPS
> for
> > the following cases:
> >
> > 1) 56 disks, 1 aggregate, RAID-DP size 16
> > 2) 112 disks, 1 aggregate, RAID-DP size 16
> >
> > I'm only interested in the total raw disk IOPS available in each case,
> > not including considering the filer head. For example, we know
> that
> > RAID-0 with 56 disks @100 would yield 5600 IOPS.
> >
> > I don't know how to do this calculation with Data ONTAP's
> implementation
> > of RAID4 or RAID-DP.
> >
> > Any assistance would help.
> >
> > Thanks
> > Suresh
> >
> >
> >
> >
> >
>
>
>