SCSI Lun question

Does anyone know how the AHA8 scsi driver deals with LUNs?
I have the following configuration set up.
A RAID with two channels has two RAID groups, which can each be thought of as a hard drive.

If I am connected to just the first channel, I boot off of LUN 0, which becomes /dev/hd0, but I do not see /dev/hd1.

To fix this I configure the RAID as follows. On the first channel, the raid groups have LUN 0 1. On the second channel the raid groups are reversed. Each RAID channel goes into a separate SCSI controller.

If the AHA8 driver only looks for LUN 0, I would expect to see /dev/hd0 and /dev/hd1 only. If the AHA8 driver checks for LUN’s other than 0, I would expect to see 4 drives /dev/hd0, /dev/hd1, /dev/hd2, and /dev/hd3, where hd0=hd3 and hd1=hd2, and of course I would only need to use one controller.

Instead I see /dev/hd0, /dev/hd1, and /dev/hd2, where hd1=hd2.
This is the default behavior of AHA8. Does anyone know what is going on?

This is using 6.3 SP2