From GoFacts

How to setup hw-raid before installing the operating system

Download the latest Diagnostics ISO Image from: Diagnostic CD burn it onto a CD and then boot this CD.

Once booted this will bring up the AIX diag which enables you to set the SCSI disk RAID settings as you like. Basically you have to modify all disks which should belong to a RAID configuration from a regular 512-byte block size to a 522-byte block size array candidate disk as only such candidate disks can be included in a RAID setting. Once the RAID settings are done, the OS will not see the single disks of the RAID setting anymore, just your RAID disks.

If you are using SUSE SLES9 you can also boot a CD or network, select "Boot a rescue system" and run iprconfig utility.