6-4
ASUS PCI-DA2200 User’s Manual
6.2
How Does the RAID Controller Work?
6.2.1
SCSI Channel, SCSI ID and LUN
A SCSI channel (SCSI bus) can connect up to 15 devices (the SCSI
controller itself excluded) when the Wide function is enabled (16-bit
SCSI). It can connect up to 7 devices (the SCSI controller itself
excluded) when the Wide function is disabled (8-bit SCSI). Each
device has one unique SCSI ID. Two devices having the same SCSI ID
is not allowed.
The figure on the left illustrates this. To file a
document into a cabinet, you must put the
document into one of the drawers. Let’s apply
this metaphor to SCSI: the SCSI ID is the
cabinet, and the drawers are the LUNs (LUN is
short for logical unit number.) Each cabinet
(SCSI ID) can have up to 32 drawers (LUNs).
Data can be stored into one of the LUNs of the
SCSI ID. Most SCSI host adapters treat a LUN
like another SCSI device.
LUN 0
LUN 1
LUN 2