Re: Raid performace issues (Raid 5 vs. Raid 0+1) with database files

Broad generalizations don't work out in the field. RAID 0+1 performs better than RAID-5 in all cases I've ever seen, but that's not a sufficient reason to use it. Oracle does an excellent job of caching it's tables. Most environments I work in there is between 4GB and 24GB of RAM available. It's quite acceptable to put the Tables and application on a RAID-5 volume because all reads are going to be from cache.

In the same regard, putting Redo, Rollbacks or temp Table Space on RAID-5 will kill your performance. Even with hardware RAID! So RAID 0+1 are the only RAID option I can recommend.

But as always, your mileage may vary. Take a baseline measurement, using 'iostat -xn' or 'vxstat'. Look for disk a_svct and b% that are measured in the 10's. If you find either, you need more disks, or to rethink how your disks are configured.

Regards,

Andrew Garman
Goliath Networks, inc. Received on Thu Sep 02 1999 - 10:26:20 CDT