Re: RAID and Oracle

David E. Daniel wrote:
> I have been attempting to perform some research regarding the use of
> Oracle in a RAID environment. The university at which I am employed is
> moving my Oracle from an Intel/NT platform to a Midrange Unix
> evironment. In the process, they are setting me up with whatever disk
> setup I desire.
> In my research, I have found out a few things.
> - Oracle states that you should not use RAID.

You may be misquoting them. I've heard recommendations NOT to use RAID5 because of its write overhead but RAID 0+1 is in common use.

> - RAID 5 works best for a data warehouse but only for DBs that are more
> read intensive.

RAID5 works well and is suited to ANY 90% or better READ requirements. RAID5 is a cheap reliability configuration, NOT a performance configuration and should be selected carefully.

RAID5 will protect against disk failure but NOT against bad block media failure where the disk block and not the disk as a whole fails.

To operate "properly" (database recovery wise) an Oracle database needs to separate CONTROL files to different disk devices, REDO Logs to a separate device(s), Archived REDO Logs to separate device, and ideally separate tables from indexes. Most RAID5 devices give you all your storage in one huge virtual disk and you cannot separate these database components without buying multiple RAID5 boxes.  

> - RAID 0 and 1 appear to be what most people are using.

More expensive than RAID5 but also more flexible for the DBA to control file placements.

DBAs need to be able to pick and choose the type of RAID (if any) required
for each database component. Why put the TEMP tablespace (high write and
read but not critical tablespace) on a slow but very reliable device?  

> What I would like to know is:
>
> - What RAID if any are you using?

All 130 Gbytes RAID5 (8 devices; here when I arrived) :(

> - How have you distributed your database files across the disk(s)? or

No control on placement within a RAID5 device but high performance files have been striped across multiple RAID5 devices.

> Are you just letting the OS handle your file storage?

What do you mean?

I plan all my database object sizing and growth.

> - What performance issues, god or bad, have you encountered?

RAID5 sucks.

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   T T T T T T T T        Bruce Pihlamae
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