Re: ORACLE8 NT and RAID5

From: <dcoan_at_aegonusa.com>
Date: Fri, 16 Jul 1999 19:16:11 GMT
Message-ID: <7mo0dg$obe$1@nnrp1.deja.com>

In article <7mnmu1$k2i$1_at_nnrp1.deja.com>,   drfuller1_at_my-deja.com wrote:
> We are currently configuring a new NT server for our Oracle8 database
> and I would like to know the pros or cons of using raid5 ot if anyone
> has a better recommendation, it would be appreciated.
>
> Thanks,
> Don
>
> Sent via Deja.com http://www.deja.com/
> Share what you know. Learn what you don't.
>

A subject near and dear to my heart...... We are Oracle 7 nd 8 on NT also.

All raids give about the same level of fault tolerance.

We recently had the opportunity to do some performance comparing of RAID levels in a real world environment using both compaq and EMC dasd. Here are the results:

Raid Level - Cycle times
Raid 5 (EMC RAID S) - 23 hours
Raid 1 (EMC) - @12 hours
RAID 10 (0+1) (Compaq) - @11 hours

We never did RAID 10 on EMC because of the minimum stripping size on EMC. However, I still think that would have given us the best performance.

We also have a Sybase serrver where performance of a query went from 1 hour to about 9 minutes by just going from RAID 5 to RAID 10. (SERIOUSLY!!) Of couse the EMC DASD costs about 10-20 times the compaq and has @5GB of cache, so we were surprised to see such a giant timing difference, but it was there and proven several several several times using several servers and Oracle configs.

DASD vendors and people will give you the old 'But everything is comming from disk Cache' and 'You don't understand how OUR Raid 5 works' and the ever famous 'let me show you this white paper' arguments. DON'T FALL FOR IT!!!!!!! Simply, tell them to prove it on your DB in your shop. Perhaps in your envinment with your DB (ie a DSS db) the performance hit will not be too bad.

In General:
Raid 5 - SLOW, least expensive
RAID 1 - Fast, More expensive
RAID 0+1 - Fastest, Same expence as RAID 1

Other RAIDs - not really worth mentioning. Avoid them.

On a RAID 5 array, performance will degrade more than on other RAIDs if a drive fails.

Bottom Line Recommendations:

- More spindles are better.
- Stripe the data across spindles.
- If you can afford it go RAID 10 (0+1) DO IT!!!
- Aviod OS level striping - Do hardware level
- Raid 1 is an ok alternative, but requires more support as far as

placement is concerned to get the performance. - Only use RAID 5 when ..... Well - Just don't unless you have NO other choice and you prove the performance is acceptable and you can live with it forever. Remember - The choice you make today becomes tomorrows 'thats we way we have always done it' and it is used everywhere.

WOW - How high can I stack this soapbox? :-) Good luck.

Doug Coan
Senior Client Server System Integrator
AEGON USA
dcoan_at_aegonusa.com

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Share what you know. Learn what you don't. Received on Fri Jul 16 1999 - 14:16:11 CDT