Re: RAID-5 and Oracle Performance

Jeff Shervey wrote:
>
> Agreed... combinations of RAID-5 with a write-back Hardware RAID controller
> and RAID-1 work good. Of course, RAID 0+1 is the absolute best all around
> RAID configuration but it's expensive because every disk is mirrored besides
> being striped. No write penalty because there is no parity kept.
> Especially when restoring a 50GB database and a VP with a stopwatch is
> looking over your shoulder wondering when the production database will be
> ready. Also, no degradation when a single RAID-5 disk goes bad or is
> offline from the Raidset.
> We are using DEC Alpha 4100 based servers with HSZ-40 (32MB Cache) and
> HSZ-70 (128MB) RAID controllers.
>
> We just received the DEC HSZ-70 Enterprise Storage Array with about 54GB of
> 9GB disk. (7 - 9GB disks) We were eating 2GB and 4GB disk up as if they
> were candy.
>
> /diskA-r5 - 54GB (9GB x 7 Disks) - Oracle data and indexes - tablespaceA -
> DatafileA
>
> My UNIX admin wants to throw our Oracle Manufacturing database on one single
> giant 54GB RAID-5 array. I don't really agree. Because Oracle data and
> indexes won't really be separated from disk drive heads. I would rather
> have 2 separate 27GB RAID-5 arrays. Example:
>
> /diskA-r5 - 27GB (9GB x 4 Disks) - Oracle data - tablespaceA - datafileA
> /diskB-r5 - 27GB (9GB x 4 Disks) - Oracle indexes - tablespaceB -
> datafileB
>
> Therefore when queries touch both the data and indexes - Physically separate
> drive heads on 2 separate arrays will not contend with one another. They
> will execute more in parallel.
>
> Does this make sense to anyone? What do you all think?
>
> jeff.sherveynospam_at_us.landisstaefa.com
> Take the nospam off my username to reply...
>
> Jeff Shervey
> Landis and Staefa - Buffalo Grove, IL
> Oracle/Ingres DBA - Oracle Financials

Well we have our Oracle DB on a RAID 5 (DG Clariions) and I have all our tablespace together on one raid 5 (~12 GB) the redo logs on 2 other drives and the rollbacks on yet another drive . Performance is good although I wish I could get the System tablespace off by itself. My biggest complaint is index fragmentation but I have a few scripts that scan the bigger indexes to check to see how fragmented they have become. I then rebuild them-as soon as we go to 7.3.x I can rebuild them on the fly (we're @ 7.2 on the UNIX boxes and 7.3.2.... on the NT side of the house). Our disk arrays do have write cache and seem to work well. I do hot backups daily to disk (then to tape) so my 12 GB DB takes about 2 hours to move disk to disk and run the logs against it to get it back into sink (depending how many archive redo logs there were generated). Tape is my LAST resort.

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