Re: ORACLE8 NT and RAID5

On 20 Jul 1999 14:36:05 GMT, "Kaboel Karso" <karso_at_kpn.com> wrote:

Good point - I have heard someone else talk about 1+0 versus 0+1. I think 0+1 referres to a grossly misconfigured system where the drive are mirrored on a single channel and stipped either on the single channel or across multiple channles. Is this what you mean by Raid 01? (BTW - I have seen this setup - Slow performance and a big issue when a drive dies.)

Also -I have seen that not all RAID 5 system's work the same. EMC for example Strips only the parity by default. Data fills up drive 1 first then drive 2 then 3. This kills performance I have not varified this, but the EMC guys setting up our system said their minimum stripping size is 1 MB. OK for a big DB but a little large for many people.

The thing i like about raid 10 is the I set up all drives on a channel to be one stripped set and then mirror to a set on another channel. This way I get the speed of having the stripped set, the speed of the controller doing interleaving and thus the mirrored set spindles, and of course the fault tolerance.

For NT, check out David Sisk's Oracle on NT home page. He does a good job of explaining RIADs and last i heard was planning to add a RAID 10 section.

I someone held my feet to the fire and said OK- You must use all RAIDs and use the least amount of disk... I would do this.

Oracle Executables - RAID 5
Data - RAID 10
Index - RAID 10
Temporary - RAID 0 (if it dies - you can recover but..... I don;t like this. Fault tolerance is cheap)
Redo - Multiple Raid 1's (this way you don't need to use multiple log group members. and ARCH can be working on 1 physical while LGWR is hitting against another physical. This takes some setup so I still I still like RAID 10 for this from a speed and ease of setup perspective)
RBS - Raid 1 or RAID 10 depending on the load. Archive Redo - Raid 10.
I would let them burn my feet before i used raid 2,3,7.

Bottom line - RAID 10 will in almost all cases outperform RAID anythingelse. You could set up a large sequential read only system and place the data maticulously and perhaps get raid anythingelse to do a little better, but for my basline setups.... Start with 10 and back away if you HAVE to is my rule.

At 3:00 in the morning when i'm on call, a system is down and I;m doing restores or some sort of surgery to fix a problem, I want all the speed i can get. I figure a my hourly rate pays for several additional drives real quick.

Well - There's my 2 cents. You get what you pay for :-). Good discussion here.

>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.
>>

Doug Coan
Senior Client Server Systems Integrator DCoan_at_aegonusa.com
"Live to Learn and Learn to Live" Received on Sun Jul 25 1999 - 11:23:12 CDT