Re: RAID 5 7+1 with oracle

I based my comments on response time. The metric that is important to me is: How many IOPS can the RAID group sustain and still provide 10ms or less response time?

// from the HP pdf

RAID 15k R/W 15k R

       IOPS IOPS
----- ------- -----

2D+2D     550   480
4D+4D    1100   990
3D+1P     390   500
7D+1P     750   925

In this case 7D+1P is better than 2D+2D. I do recognize that we are comparing 8 spindles to 4, but the observation is true.

Say you compare the 4D+4D to 7D+1P. At 10ms the IOPS are nearly identical for reads, but for the R/W IOPS the "RAID penalty" is observed (725 vs. 1100).

For the data warehouse space this "write penalty" may be acceptable. The reason being data is generally loaded once (many times in isolation) and queried many times.

I don't want to get too caught up in the low level stuff because my experience is this: RAID5 can provide comparable (or better) performance to RAID10 at a cheaper price.

On 10/5/07, Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk> wrote:
>
> I'm not convinced your interpretation of the graphs is correct.
>

-- 
Regards,

Greg Rahn
http://structureddata.org
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