Disk / datafile configurations

[JMac]

We've all heard of the ideal 21 disk solution but what is the bare minimum number of seperate physical disks (and don't say 1!!) you can use before performance is severely hindered.

Our Network Admin has just bought a huge new box for a new database (I wasn't involved!) and it has 8 disks. Using RAID for multiplexing means I have just 4 disks available for placement of datafiles. In reality I'll have just 3 as Disk1 will be for system files.

What can I do with 3 disks? Is this still an issue these days now we've got super fast processors? What arguments can I make for us buying additional disks?

[bensr]

The answer may be not that simple as you would like to see.
Maybe there are some articles on the net, so you should search for them. Some things also depends on the kind of database-use OLTP or batch-processing, large tables/ indexes
(partitioning).
There is also the machine itself. Are disks placed in stripes,
is there load-balancing on operatingsystem level.
What differences are there between logical volumes and physical volumes?

Main point is: Disk reading/ writing is a very time consuming event, it is mechanical. The less the heads should move over the disks, the faster it responds.
For instance, seperate the tables and the indexes, so it does not have to reposition all the time from index to table etc.
Create another tablespace for RBS.

I know it's not a complete answer, but at least you have some points to think over.