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FC to SCSI Mapping
Introduction
Your ADIC Scalar 218FC provides connectivity between Fibre Channel devices and SCSI devices. FCP and
SCSI systems employ different methods of addressing devices. This appendix provides an overview of the
addressing methods of both protocols, and the methods used to translate addresses of one type into addresses
of the other type.
SCSI Device Addressing
The SCSI bus establishes bus connections between devices. Targets on the SCSI bus may internally address
logical units (LUNs). The addressing of a specific SCSI device is represented by the
BUS:TARGET:LUN
triplet. The SCSI bus allows for up to 16 devices, with up to 8 LUNs per target. The initiator uses a SCSI ID,
so typical configurations have up to 15 target IDs available for use.
BUS identification is intrinsic to the configuration: a SCSI device is attached to only one bus. Target
selection is handled by bus arbitration. Target addresses are assigned to SCSI devices directly through some
means of configuration, such as a jumper, thumb-wheel, or other setting. LUN selection is by means of the
IDENTIFY
message, which occurs after target selection.
Fibre Channel Device Addressing
Fibre Channel devices connected to a fabric—any case where 2 or more ports are directly communicating via
switch or arbitrated loop—are addressed by a unique port identifier. This identifier is assigned to a port
during certain well-defined states of the FC protocol. Individual ports are allowed to arbitrate for a known,
user-defined address. If such an address is not provided, or if arbitration for a particular user address fails, the
port is assigned a unique address by the FC protocol. This address is generally not guaranteed to be the same
value between instances. Various scenarios exist where the
AL_PA
of a device will change, either after
power cycle or loop reconfiguration.
The FC protocol also provides a logical unit address field within command structures to provide addressing
to devices internal to a port. The
FCP_CMD
payload specifies an 8 byte
LUN
field. The
FCP_CMD
element is the first element of an exchange in FC protocol. Subsequent identification of the elements of the
operation between devices is provided by the exchange identifier. This includes the
FCP_XFER_RDY
,
FCP_DATA
, and
FCP_RSP
frames.
Summary of Contents for Scalar 218FC
Page 1: ...Installation and Operating Guide Scalar 218FC Library...
Page 6: ...vi Blank Page...
Page 101: ...Diagnostics Menu 91 Blank Page...
Page 105: ...Error Codes 95 Blank Page...
Page 123: ...113 Index...