Re: ORACLE8 NT and RAID5

hi,

RAID0 	= striping
RAID1	= mirroring
RAID2	= duplexing
RAID5	= striping with calculation of the parity bit placed on all the disks
participating in the raid volume using these in a round robin fashion
RAID10	= striping & mirroring

Saying that, you should investigate what the different raid levels is actually doiing. For performance reasons RAID0 is preferrable. As for reliability, you must have some sort of protection. The best scenario is using RAID10 (RAID 1+0). btw, there is a difference between RAID 0+1 and RAID 1+0 , not performance wise but in case of a disaster.

Imo, the next best scenario is to use RAID5 for the datafiles and place all other files causing sequential writes e.g the redo logfiles, on a non raided disk. The redolog files preferrably mirrored by Oracle.

I found some whitepapers on this topic on the SUN website a while ago. Maybe they're still available.

Kaboel

dcoan_at_aegonusa.com schreef in artikel <7mo0dg$obe$1_at_nnrp1.deja.com>...
> In article <7mnmu1$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
>
>
> Sent via Deja.com http://www.deja.com/
> Share what you know. Learn what you don't.
>
Received on Tue Jul 20 1999 - 09:36:05 CDT