Scsi Tid Maps For Fibre-Channel Adapters - Hitachi Universal Storage Platform V Configuration Manual

SCSI TID Maps for Fibre-Channel
When an arbitrated loop (AL) is established or re-established, the port
addresses are assigned automatically to prevent duplicate TIDs. With the SCSI
over fibre-channel protocol (FCP) there is no longer a need for target IDs in
the traditional sense. SCSI is a bus-oriented protocol requiring each device to
have a unique address since all commands go to all devices. For fibre channel,
the AL-PA is used instead of the TID to direct packets to the desired
destination. Unlike traditional SCSI, once control of the loop is acquired, a
point-to-point connection is established from initiator to target. To enable
transparent use of FCP, the SGI IRIX system "maps" a TID to each AL-PA.
The host maps SCSI protocol to fibre-channel protocol and detects and
accesses fibre-connected devices using device files (/dev/dsk/c*t*d* and
/dev/rdsk/c*t*d*) in the same way as for SCSI-connected devices. The device
files for fibre-connected devices are configured in a different way than SCSI-
connected devices because fibre supports 126 addresses per path while SCSI
supports 16 TIDs per path.
Table A-1 identifies the fixed mappings between the TID (drive) values
assigned by the IRIX system and the FC native addresses (AL_PA/SEL_ID) for
FC adapters. The controller number (the dks value in /dev/dsk/dks*d*l*s*)
depends on the server configuration and a different value is assigned per each
column of Table
Note: The mapping defined in
following conditions:
When USP V devices and other types of devices are connected in the same
loop.
When information for unused devices remains in server system.
When multiple ports participate in the same arbitrated loop.
Hitachi Universal Storage Platform V/VM Configuration Guide for SGI
A-1.
Table A-1

SCSI TID Maps for Fibre-Channel Adapters

Adapters
cannot be guaranteed under the
® ®
IRIX Host Attachment
A
A-1