Re: Spindles and big disks

In article <TRWx4.905$mF1.31922_at_news.uswest.net>,   "KineticGuy" <nospam_at_spam-world.usa> wrote:
> I grew up on the philosophy that databases perform better with more
 spindles
> and by isolating hot areas to their own groups. This concept still
 makes
> sense to me.
>
> Now the minimum disk sizes available are 9 GB and hardware caching is
 the
> hot thing. What are folks doing with this issue when sizing new
 systems.
> If you have a 40GB database, it's getting harder to justify the costs
 for as
> many spindles versus the old 1GB - 4GB days.
>
> I'm interested in thoughts that people have on this.
>
>

I love talking DASD and databases. Here is my two cents

• If you are using RAID 5 don't worry about it. You are screwed anyway. :-)
• Use Raid 1 at a minimum and raid 0+1 is by far the best for performance. (regardless of caching method)
• Cahcing does help considerably, but you need to be aware of were the cache is. Smaller controller side cache can outperform larger Disk side cache due to the trips it has to take across the SCSI channel.
• More spindles are better, but the performance gains of 5-6 versuses 10-12 'may' not be significant. A lot of DB access is random I/O of small chucks. You may not be able to get all 10-12 going at once anyway.
• DASD is getting cheap. (unless you are buying EMC) I can throw up a 100GB raid 0+1 array for about $16K.

Bottom line - it depends on your environment. It your DB is 50, 100, 200 GB you may not need to worry about spindles if your RAID is correct. If you have a 500GB, 1TB or more, well then thats a horse of different color. You'll need all the tricks here.

Good luck....

--
Doug Coan
Oracle Certified Professional DBA
AEGON USA
dcoan_at_aegonusa.com


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