SAS scsibus target numbering

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

I have a (mpt) SAS with seven discs connected.
The discs attach as sd0..sd6, but the SCSI target numbers are 0..5 and 7.
It appears to me that someone is skippig ID 6 for the controller.
It doesn't hurt too much, but it took me a while to find out why detaching 
targets 2, 3, 4 and 5 worked and 6 didn't (of course, 7 worked).

Is there a reason for this behaviour?