Re: RAID and Oracle

Stephen A. Rodgers wrote:

>
> We're about to implement a data warehouse of around 300 Gig on Oracle
> running Sun Solaris. We intend to run the data warehouse on RAID-5.
> I've run some smaller databases which were OLTP in nature, performing
> financial and HR application work on HP-UX boxes with RAID-5 in the
> past, and these performed very well. The only time I ever saw any
> slowdown was during major loads or imports. And that was not terribly
> significant. So, I would agree that the only performance hit you will
> see will be doing writes. From what I have read in the past, Oracle
> recommends that OLTP databases use mirroring and read intensive
> databases like warehouses can take advantage of RAID-5.
>
> RAID-5 can also create some performance benefits. One of the things I
> like about it is that you can automatically stripe your data across
> volumes, without having to tell Oracle to do it. It's kind of an
> automatic benefit. You don't really even need to worry about
> separating your tables from indexes since this is somewhat automatic
> under RAID-5. Of course, I separate them anyway to make maintenance a
> little easier. If you take further advantage of the striping feature,
> you can use Oracle's parallel query option to divide up processing of
> queries across disks. This fits very nicely into the RAID-5
> environment and for something like a data warehouse, can deliver some
> pretty good performance benefits.
>
> Best of luck to you. Let us know how it works out for you.
>
> Stephen A. Rodgers
> Prominence Consulting, Inc.

 RAID-5 does not automatically seperate tables from indexes. If you place your tables and indexes in seperate tablespaces, but the datafiles are in the same RAID channel, they will be placed on the same physiacl platters. However since you need a minimum of 3 platters to do RAID 5, the part of the index you need at a specific time may be on a separate platter then the part of the table you which to access at the same specific time. But this cannot be guaranteed. Received on Wed Jun 25 1997 - 00:00:00 CDT