HP XP10000, XP128 manual Scsi TID map for Fibre Channel adapters

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.

Disk array device emulations 71