Re: RAID-5 and Oracle Performance

Hi,

I am sharing my system setup details and experience with you. May be you'll find some points useful.

I have a similar setup as yours - 4 nos 8400s, 5 2100s, 1 4100 etc., with 3 boxes of SW500(HSZ40), 1 no. SW800(HSZ50), 1 no. SW600(HSZ70)(recently acquired). 8400s have RAM ranging from 1-4 GB. I have a distributed OLTP database of about 200 GB with some of the databases growing at over 100% per annum. About a year back we started using 9 GB disks as we were running out of storage shelves and space in our storage works boxes. And we are planning to shift rest of our databases on to 9 GB disk raid sets. We are also planning a shift to fibre channel based controllers.

Some of our storage boxes have upto 4 controllers which can be connected to one or more m/cs. It would actually make sense putting tables and indexes on different controllers, if possible. However on our SW500s(with dual redundant controllers) we did try to separate the indexes and tables on to different raid sets (although we did not test whether it made any difference in performance).

Different chunksize at raid controller level while initializing the raid set did make a difference. We had carried out some tests (way back in 1995) on different chunksizes. Raid set defined with a particular chunksize(I don't remember the exact figure - 32 bytes may be) gave better perfomance. May be you could try to do the same (finding out which chunk size is better for your environment).

For backups, last year, we acquired an automated tape library TL893(if I remember correctly) which has 3 TZ89 drives and can store 264 compact IV 35/70 GB cartridges. It can backup upto 50 GB per hour. We take hot online backup our databases daily (24x7 problem). I also try to keep about 4 days of archive on the disks(to save time on retrieving archives from tape during a crisis) - databases may generate upto 10-12 GB of archive per day.

I would also suggest a database block size of 8 KB for Oracle (we are running 7.2/7.3/8.0).

I hope this helps,
Ajit

In article <6aqk1e$2l2_at_news.us.landisstaefa.com>,   "Jeff Shervey" <jeff.shervey_at_us.landisstaefa.com_spamblock> 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

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