Re: RAID Performance Issue with Oracle

Peter Marusek wrote:
>
> I was told in Oracle school that RAID devices were not suitable for
> Oracle databases. Can anyone quantify the performance issues here?
> thanx
> Peter Marusek
>

There are some points to keep in mind when you install ORACLE on a disk array. Putting everything on a RAID5 stripe without a write cache will usually not provide satisfactory database performance. Write operations to a RAID5 stripe are more expensive than writes to a single disk.

In particular, the database redo log files should be on a single disk or a mirrored pair (RAID 1), NOT on a RAID 5 disk array. If the log file is on a RAID 5 array, your system's performance may be very adversly affected.

The operating system should also be on a single disk or on a mirrored pair (RAID 1). The operating system is very transaction-oriented and it may slow down a disk array's performance dramatically.

Other files that you should consider locating on a single disk or a mirrored pair (RAID 1) are temporary tables, rollback segments, and frequently updated indexes and tables.

Oracle is a memory-intensive database, with much of the random writes done in memory (SGA). Using a disk array that allows for various RAID levels (0,1,3,5,0/1) and that is configured with write-cache can give good performance as well as protection from disk failures.

On top of that, using a disk array such as DG's CLARiiON Array, a hot spare can be configured so that array rebuilds will be done on the fly. For more information on the CLARiiON, check out our web page: http://www.dg.com Received on Wed Feb 28 1996 - 00:00:00 CET