RE: DB RAID Setup

Personal opinion here, but weighted by years of doing this job. The only raid method that I've become comfortable with is raid 1+0 or RAID 10. This is mirroring where there are two copies of the data on two separate spindles. It is the easiest to implement at the OS level and performance wise. Yes, raid 5 does make more of the disk space "available" to the os and consequently the database, so it "appears" to be less costly, but Raid 5 does have to "compute parity" for the spare drive so that in the event of a disk failure the system can continue to run, although at a reduced rate because of the reconstruction that has to happen for the failed disk. Problem, what do you do when 2 or more disk fail in quick succession, OOPS. Sure this can happen in a raid10 setup, but much less likely. Also with raid 10 you can put the database into hot backup mode, split the mirrors, reset the db, and continue with life while the backup happens in the background using the split out mirror. Afterwards you re-join the mirrors & they sync quickly.. Pretty darn close to a cold backup at no extra cost, depending on your san vendor. You can't do that with RAID5.  

Dick Goulet
Senior Oracle DBA
PAREXEL International
978.313.3426
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From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Rob Dempsey Sent: Tuesday, November 18, 2008 12:06 PM To: oracle-l_at_freelists.org
Subject: DB RAID Setup

Hi  

Oracle 10g2 (data warehouse)  

I thought I would ask peoples' thoughts on the following.  

I have setup our database whereby the index tablespace and data tablespace are separate. This is not for performance reason only for ease of maintenance.  

We are being advised by the SAN provider to use the following RAID layout  

                Archive redo Logs            - RAID 10

Redo Logs                           - RAID 10

Temp tablespace             - RAID 10

Undo tablespace              - RAID 10

Index tablespaces           - RAID 10

System tablespace          - RAID 5

Data tablespaces              - RAID 5

 

Redo logs / Temp tablespace I agree with.  

To use RAID 5 for data, I understand there is a write performance hit but this is a data warehouse so should be ok (Ideally I would like that RAID 10 as well). But to have the index tablespace on RAID 10 and data tablespace on RAID 5 I found that strange. When I asked the reason why I was give the response 'that is what Oracle recommends'.  

Has anyone heard this before?  

Rob          

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