Yes. I have seen the penalty hit a "knee" when their are a lot of reads
also. If there are a lot of random reads at one time (typically a large
result set) it "floods" the IO on the disk system and hurts performance of
others also. This is especially true where people purchased 9 or 18 gig
hard drives and only have 3 drives for the RAID 5. They are buying for
space and not for performance.
Jim
"Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message
news:976372921.4341.0.nnrp-10.9e984b29_at_news.demon.co.uk...
>
> Good question -
>
> The answer is that a very large number of systems
> are just small office systems that have one little
> black box with a couple of CPUs, 5 discs at 9GB,
> running NT.
>
> With minimal tuning they can run perfectly well
> despite a nominal (rarely actual) overhead of 200% on
> writes, because Oracle simply avoids lots of write
> requests (even on logs).
>
> Unless the number of spindles is too low, a simple RAID-5
> system on the typical 5-disk set-up will perform perfectly
> adequately for a low-stress system.
>
> (See my book - Chapter 10 Files, Raw and RAID).
>
> --
> Jonathan Lewis
> Yet another Oracle-related web site: http://www.jlcomp.demon.co.uk
>
> Practical Oracle 8i: Building Efficient Databases
>
> Publishers: Addison-Wesley
> Book bound date: 8th Dec 2000
> See a first review at:
> http://www.ixora.com.au/resources/index.htm#practical_8i
> More reviews at: http://www.jlcomp.demon.co.uk/book_rev.html
>
>
>
> Niall Litchfield wrote in message <90tbvl$jlo$1_at_soap.pipex.net>...
> >I agree that that is what happens, and that it is wrong. however I'd be
> >interested to know exactly what sort of performance hit one gets from a
> >machine with data & indexes on raid 5, but with well tuned memory
structures
> >etc.
> >
>
>
>
Received on Sat Dec 09 2000 - 09:52:31 CST
