For Ultra 250 systems, there are two internal SCSI busses. The device "scsi" refers to the internal SCSI I/O bus for internal disk.
The following shows the output of a devalias command on a Sun Ultra 250 UPA/PCI system.
ok devalias disk5 /pci@1f,4000/scsi@3/disk@c,0 disk4 /pci@1f,4000/scsi@3/disk@b,0 disk3 /pci@1f,4000/scsi@3/disk@a,0 disk2 /pci@1f,4000/scsi@3/disk@9,0 disk1 /pci@1f,4000/scsi@3/disk@8,0 disk0 /pci@1f,4000/scsi@3/disk@0,0 disk /pci@1f,4000/scsi@3/disk@0,0 scsi /pci@1f,4000/scsi@3 cdrom /pci@1f,4000/scsi@3/disk@6,0:f tape /pci@1f,4000/scsi@3/tape@4,0 pcia /pci@1f,2000 pcib /pci@1f,4000 pci0 /pci@1f,4000 flash /pci@1f,4000/ebus@1/flashprom@10,0 nvram /pci@1f,4000/ebus@1/eeprom@14,0 parallel /pci@1f,4000/ebus@1/ecpp@14,3043bc net /pci@1f,4000/network@1,1 ebus /pci@1f,4000/ebus@1 i2c /pci@1f,4000/ebus@1/SUNW,envctrltwo floppy /pci@1f,4000/ebus@1/fdthree tty /pci@1f,4000/ebus@1/se@14,400000 ttya /pci@1f,4000/ebus@1/se@14,400000:a ttyb /pci@1f,4000/ebus@1/se@14,400000:b rscctl /pci@1f,4000/ebus@1/se@14,200000:sspctl rsc /pci@1f,4000/ebus@1/se@14,200000:ssp ttyc /pci@1f,4000/ebus@1/se@14,200000:ssp ttyd /pci@1f,4000/ebus@1/se@14,200000:sspctl keyboard! /pci@1f,4000/ebus@1/su@14,3083f8:forcemode keyboard /pci@1f,4000/ebus@1/su@14,3083f8 mouse /pci@1f,4000/ebus@1/su@14,3062f8 name aliases