Scsi Tid Map For Fibre Channel Adapters - HP XP1024 System Configuration Manual

SCSI TID map for Fibre Channel adapters

When an arbitrated loop (AL) is established or reestablished, 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, when control of the loop is acquired, a point-to-point connection
is established from initiator to target. To enable transparent use of FCP, the operating
system maps a TID to each AL-PA.
The host maps SCSI protocol to Fibre Channel protocol and detects and accesses Fibre
Channel-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
Channel-connected devices are configured in a different way from SCSI-connected
devices, because Fibre Channel supports 126 addresses per path while SCSI supports
16 TIDs per path.
The following table identifies the fixed mappings between the TID (drive) values assigned
by the operating system and the Fibre Channel native addresses (AL_PA/SEL_ID) for
Fibre Channel 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.
The mapping cannot be done when these conditions exist:
• disk array devices and other types of devices are connected in the same loop
• information for unused devices remains in the server system
• multiple ports participate in the same arbitrated loop
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Disk array supported emulations