And I was right. ignoredisks has been added to let the installer ignore SAN disks as well as for cluster setups. multipath has been added to handle dual HBAs cases where the same disk will be seen over two different paths.
Update: except ignoredisks, there is really not much you need to do but boot the Linux kernel with the option 'mpath'. The multipath option lets you set/configure the multipath.conf configuration, I believe. Not used yet. In my case, I use this line to boot Linux and start a kickstart installation:
linux mpath text nousbstorage ksdevice=eth0 ks=http://server/mpathks.cfg
That's it. The first activates multipath-aware option in anaconda. The second uses text mode. The third parameter skips any USB devices in my PowerEdge 2950 (virtual floppy, disk and cdrom). The fourth selects a NIC to use during installation, otherwise you get a screen to select one from.
I use a sample kickstart file from the Oracle Wiki that listed the minimum required packages for a working server that can run Oracle databases. I'm actively trying to maintain that file in the wiki. The original kickstart file only worked for OEL/RHEL 3/4. Some packages have disappeared in release 5 of the OS.
Update: here is the Red Hat documentation of kickstart in Enterprise Linux 5.3
Update2: There are also similar pages for kickstart options in RHEL 5.4 and 5.5