HP Surestore Disk Array 12h SGI IRIX Configuration Guide - Page 47

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 SGI IRIX 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. Table 6 (page 48) identifies the fixed mappings between the TID (drive) values assigned by the IRIX 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 of Table 6. The mapping defined in table 10 cannot be guaranteed under the following conditions: • when disk array devices and other types of devices are connected in the same loop • when information for unused devices remains in the server system • when multiple ports participate in the same arbitrated loop Disk Parameters 47