I've found not all systems scan the same direction. :-/ I can't recall which way the A3000 SCSI does it.
The 3k scans bottom up (0 through 6). I've got my HDD on ID1, so I can hook up a drive on ID0 and have it automounted w/o fiddling around.
btw: all narrow SCSI drives I've seen provide a way to turn on/off the termination option. Old drives require you to add/remove the terminator packs, newer drives with active terminators got a jumper.
However, more modern LVD/SE drives (U2W+) have no termination options any more.