RE: DB RAID Setup
- From: "Goulet, Richard" <Richard.Goulet@xxxxxxxxxxx>
- To: <Rob.Dempsey@xxxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 18 Nov 2008 13:05:37 -0500
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@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Rob Dempsey
Sent: Tuesday, November 18, 2008 12:06 PM
To: oracle-l@xxxxxxxxxxxxx
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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