I/O Interfaces
Parallel SCSI
ABCs of SCSI Addressing
SCSI
Data/Address Bus
Initiator
T
T
e
e
rm
rm
Host
i
n
i
n
ator
ator
Bus
Adaptor
Control Signals
ID7
Interface Interface Interface Interface
SCSI SCSI SCSI SCSI
RAID Tape Disk RAID
ID0 ID4 ID5 ID6
LUN 0 LUN 0 LUN 0 LUN 0
LUN 1 LUN 1
LUN 2 LUN 2
LUN 3 LUN 3
Address = BUS : Target ID : LUN
Physical disk drives and tape drives do not support Logical Units so they
always use the address of LUN 0 in order to keep the addressing format
consistent.
Disk subsystems do support Logical Units, so this is how we provision storage
to multiple hosts, each having access to unique disk blocks on to which they
store data.