Yellow Dog Linux

OK, got YHC on my cluster and have a quick question. I'm running a headless XServe as the headnode and have all three drive bays filled with 80G drives. I removed the second and third one when setting them up just had /dev/sda* for YDL. Now, I'd like to use /dev/sdb* for automated backups, etc but have run into a small problem. The drive I intend to use has 10.4 on it and even with yaboot defaulting to ydl, if I start the machine up with sda=ydl and sdb=osx, osx is booted. Moreover, if I boot ydl and then insert the osx drive, it is not recognized (e.g., not powered up). fdisk /dev/sdb doesn't recognize it as being there. How do I tell the scsi subsystem to recheck its system? or more generally, how do I hotswap non-system discs?