Need advise about expanding storage

Hello

I am running an Oracle DB (8.1.7, Unix). All Oracle data is contained in three independent devices. It happens that three devices are to few to cope with the numerous I/O that Oracle does to different datafiles and that could be done in parallel.

The question ist: How should be a Raid system configured to be used with the DB? It is a StoreEdge A1000 (SCSI) with 12 HD that is able to be setup in different Raid flavours.

I first thought that just making one device out of it by striping data over all 11 harddisks (1 is for parity) would be fine, since that would accelerate access a lot. But since Oracle will be trying to access different files more or less at the same time, having one device would force serializing access to it. OK, access will be fast, but can only happen one after the other.

Another possibility would be to make one device (or LUN) out of each harddisk, so access to each particular harddisk won't be so fast, but it can be done in parallel, since each harddisk behaves independently.

Perhaps a kind of compromise between these two extreme cases would be the optimal solution, that is, building several groups of harddisk which use stripes but behave as independent devices.

Well, having three copies of the controlfile, five redolog groups with two members each and running in archivelog mode demands a minimum number of 6 devices, without considering the access requirements for the datafiles containing the real data.

One hint, however: The datafile in the index tablespace shows a much larger number of read/write access compared with other datafiles, and the main datafile containing most objects is mainly being read, but seldom written to (data mining application).

Need some advise, since I am not that experienced with performance issues due to the physical topology of the database.

Thanks a lot
Rick Received on Thu Jun 06 2002 - 16:54:57 CDT