This is a known problem. Default Red Hat 9 installer does not support Adaptec AIC-7902 Ultra320 SCSI controllers that's integrated on many high end server motherboards. Even though the kernel does have support for the controller.
What you need to do is to build a special install boot disk using Red Hat's updated kernel.
Also, which motherboard is this? I have a set of RH9 CDs that will install on the following boards with AIC-7902 controllers
Intel SE7501WV2
Tyan S2721UGN-533
The motherboard is: Intel SRSH4 A60891-603 (New version, for U320 SCSI)
I have Kernel of 2.4.21, and I compiled the module aic79xx.o, but I really dont know how to install RH9 with my new compiled module. Could you help me?