Well, for starters, if you really have a useful 80GB database (2 x 2 40GB RAID 0/1) will cost matter?
I can always find SCSI drives for about $200 at Fry's electronics. Last time I looked they had 9 GB 10K RPM IBM SCSI II's or U160s (I forget exactly). My own server has modest 4.5 GB IBM SCSI II drives in it that I picked up for $180 just as they were being phased out for the 9 GB drives.
Integrated SCSI on a motherboard sets you back $150 or so. So two SCSI platters in a RAID 1 configuration and on-board SCSI is doable for $600 or so.
IDE is fine for one or two disks (on separate IDE channels), if you get a brand/model that works reliably in UDMA mode. Promise IDE controllers now work with Linux though I'm not sure the code's in commercial distributions yet (you may have to find the appropriate patches/drivers yourself). This starts looking attractive, because it's easy and relatively cheap to add a Promise IDE controller, pick up two more channels, then have four platters each on its own channel (assuming your box's CD Rom is off most of the time, and in any case the disk will be slave not master).
