This is part of a NetBSD/sun4m configuration file:

# SCSI bus layer.  SCSI devices attach to the SCSI bus, which attaches
# to the underlying hardware controller.
scsibus0 at esp0
scsibus1 at esp1
scsibus2 at esp2

# built-in SCSI
sd0     at scsibus0 target 0 lun 0
sd1     at scsibus0 target 1 lun 0
sd2     at scsibus0 target 2 lun 0
sd3     at scsibus0 target 3 lun 0              # internal disk

# FSBE/S #1
sd4     at scsibus1 target 0 lun 0
sd5     at scsibus1 target 1 lun 0
sd6     at scsibus1 target 2 lun 0
sd7     at scsibus1 target 3 lun 0

# FSBE/S #2
sd8     at scsibus2 target 0 lun 0
sd9     at scsibus2 target 1 lun 0
sd10    at scsibus2 target 2 lun 0
sd11    at scsibus2 target 3 lun 0

# These entries find devices on all SCSI busses and assign
# unit numbers dynamically.
sd*     at scsibus? target ? lun ?              # SCSI disks
st*     at scsibus? target ? lun ?              # SCSI tapes
cd*     at scsibus? target ? lun ?              # SCSI CD-ROMs
ch*     at scsibus? target ? lun ?              # SCSI changer devices


No, I don't have this many disks right now, but I wanted to make sure that
if one did die (or just got removed), the others would not move and screw
up /etc/fstab. I also have a configuration with two SCSI busses where the
drives are allocated with even drives on bus zero, and odd drives on bus
one (I was of two minds about that one).