User`s guide

StorageWorks SCSI Buses
5.2 SCSI Bus Length and Termination
5.2 SCSI Bus Length and Termination
Two important considerations for all SCSI buses are bus termination and bus
length.
• Each bus requires a terminator. The terminator (T) and jumper (J) connectors
are mounted on the rear of the backplane.
• Table 5-2 defines the maximum lengths of the StorageWorks SCSI buses as
measure between the two bus terminators.
Table 5–2 SCSI Bus Parameters
Bus Type Transfer Rate Meters Feet
8-bit, single-ended 5 MB/s 6 19.7
8-bit, single-ended 10 MB/s 3 9.8
16-bit, differential 20 MB/s 25 82
See Section 5.3 for detailed discussion of shelf SCSI bus lengths.
• The total length of the SCSI bus is critical. The components of bus length are
as follows:
– Shelf backplane
– Controller backplane
– SCSI cables connecting the host, the controller, and the SBB shelf
• The length of the SBB shelf SCSI bus is measured from the input connector,
JA1 or JB1, to the bus terminator.
Note
Adding or removing devices to a shelf does not change the length of the
shelf bus. The only way to change the length of the shelf SCSI bus is to
reposition the terminator.
5–4 StorageWorks SCSI Buses