Yes, SCSI can be 'pretty wierd' at times. In a nutshell, there are a total of 8 SCSI IDs on a SCSI bus (as I recall off the top of my head). These IDs are 0 - 7. Often the 0 ID is reserved for the 'host adapter' which is tyically the bus interfaced card. (someone please correct me if I've misstated the ID info).
The more tricky, and often fatal problem that come with SCSI, is the requirement to have electrical terminations at both ends of the bus. All devices between the two ends must not be terminated. This can cause real nightmares for people. Sometimes you get all the SCSI IDs just right, but in rearranging things on the bus, you forget to readjust your terminations and WHAM!
Sometimes it will boot just fine and run until a intense transfer on the bus causes the OS to panic (hang up and die). Sometimes even correctly configured devices and terminations can cause unexpected errors.
BTW: I used to be a very big fan of SCSI but (as you can read); I've moved to EIDE for most server applications. I have found EIDE to be 'fast enough' and more reliable. However, for fault tolerant applications (like CPU switchover and other complex RAID configurations) SCSI provides good bus flexibility. Depending on your application, carefully consider the complexity of SCSI vs. the simplicity of EIDE before making a purchase.