the adabtec 1200A appears to be a "fake" raid controller consisting only of an ata controller with a bios. the hardware responsible for the raid function seems to be missing. therefore, linux sees right through the bios detecting the single hard drives.
most of the cheaper so called raid controllers, sata as well as pata, appear to be this kind of semi raid controllers where software is handling the raid functionality. i experienced this with cmd, sis, via, promise, adapdec both pci and on board controllers.
if you are lucky a software functionality is included in the kernel (ATA/IDE, support for ide raid controllers in the 2.4 kernel) but its at this time experimental and never worked for me so far. this type of software functionality should not be mistaken with the "real" softare raid, also called multible devices driver support.
rarely there is a source code for drivers on the web which can be compiled and included during setup. raid utility software is also hard to find.

i can give a short introduction how to get a via "raid" controller to work.
download the latest drivers from viaarena.com.
compile the modules for the kernel of the corresponding setup CD and put it on floppy. when installing linux switch to console just before choosing to manually partition the device. mount the floppy and ismod the raid module. mknod a /dev/sda device if absent. this worked for 64 bit redhat fedora 1 and a via vt8237 sata raid controller. be aware to recompile the module for whatever kernel you want to use later on. load it at boot-time if root is on that raid. i strongly recommend grub. btw: scsi support is needed as well (sata). you may need a mkinitrd --preload=via_raid_module. but be aware, the performance is worse than bad, at least in my case where a (hdparm -tT) 60mb/s single drive had only 10mb/s as "hardware" raid 0 with two of those disks.
conclusion: in your case you may want to use software raid.
please correct me if i'm mistaken. i like to improve my knowledge as well.
