Re: Oracle RAID

michael.pawle_at_ncom_main.ccmail.ncom.nt.gov.au writes:

>How is ORACLE (v7.1.6) best configured on RAID5?

There is no single answer to this, it will vary depending on your system and data requirements. Give yourself several weeks to experiment with the RAID system before settling on a final configuration. (I ran tests for over 3 weeks, including a full parallel test one weekend.)

>What is ORACLE performance like on RAID5 compared to a conventional
>implementation over multiple disks?

This will also vary. In tests with identical databases, one on two 2G drives, one on two RAID5 systems sharing a single controller, RAID5 was about 10% faster for us in a mostly 'read' test, and more like 20% faster in a test with a lot of database updates. (Mostly because of writethrough factors.)

With faster SCSI channels we could probably improve on that, especially the read times, but our systems vendor doesn't support FAST/WIDE yet, even though the RAID drives do.

After reoptimizing the database, mostly moving tables and tablespaces around and rebuilding indexes, and spreading the datafiles over a larger number of 'drives', both normal and RAID, we were able to take one batch job from around 5 1/2 minutes to under 3 1/2 minutes. All of our users commented on the improved performance the day we converted.

>Should ORACLE's online redo log files and control files be mirrored on RAID5?

Yes, although I don't currently do it for the online redo files, which are on the RAID drive. (I should.) Multiple control files is a MUST, even with RAID.

>Should ORACLE's archivelog mode be switched on at all (as RAID5 protects
>data from loss)?

RAID5 doesn't protect you from all forms of data loss. For example, if someone drops an important table, how will you recover it without archive logs?

>Would it be best to have a mix of RAID5 and non RAID disks so that log
>and control files can physically exist in 2 places?

This doesn't require a mixture of RAID and non-RAID, though you can certainly do it that way, as we did. Keep in mind that Oracle doesn't KNOW a particular drive is a RAID drive. On our system we keep all the Oracle datafiles except for the TEMPORARY and RBS tablespaces on RAID drives, those and the Oracle executables are on the regular drives.

>Where should Oracle Finacials out and log files be placed given a mix of
> RAID5 and non-RAID disks?

Not having Financials, I can't answer this, but you will probably have to experiment to find the best configuration yourself no matter what kind of applications you are running.

---
Michael Nolan, Sysop for the DBMS RoundTable on GEnie
nolan_at_tssi.com, dbms_at_genie.com, nolan_at_inetnebr.com
(posted from nolan_at_helios.unl.edu)