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How the RAID Controller Works?
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 owning the same SCSI
ID is not allowed.
The figure on the left is a very good example. If you are to file
document into a cabinet, you must put the document into one of the
drawer. From a SCSI's point of view, a SCSI ID is like a cabinet, and
the drawers are the LUNs. Each SCSI ID can have up to 8 LUNs
(Logical Unit). Data can be stored into one of the LUNs of the SCSI ID.
Most SCSI host adapters treat a LUN like another SCSI device.
In firmware versions 2.11 or later, each SCSI ID can
support up to 32 LUNs.
Chapter 6 Configuring RAID
LUN 0
LUN 1
LUN 2
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