– Use a maximum system-to-device cable length of 5 m (17 ft) to attach to the host interface board
(SCSI) and three to six daisy-chained drives.
Note: For maximum performance, it is recommended to have a maximum of one drive per SCSI
bus.
– Only use the maximum system-to-device cable length of 25 m (82 ft) to attach directly to one device
(a point to point interconnection).
Note: Daisy-chaining is NOT recommended because of potential issues with SCSI bus performance,
SCSI cables/connectors, and host bus adapters.
Physical characteristics of the SCSI interface
The library operates as a set of SCSI-3 devices. The Ultrium tape drives attach to servers with an LVD
Ultra160 SCSI interface. Each SCSI drive sled uses shielded, HD68-pin connectors, and attaches directly to
a 2-byte-wide SCSI cable.
Any combination of up to two initiators (servers) and up to four targets (devices) is allowed on a single
SCSI bus if the following conditions are met:
v The SCSI bus is terminated properly at each end
v Cable restrictions are followed according to the SCSI-3 specification
Under the SCSI-3 protocol, this type of attachment allows cable lengths of up to 25 m (81 ft) with the
appropriate cable and terminator. The table gives the maximum bus length between terminators for the
LVD interface. For information about cable connectors, see “SCSI connectors and adapters” on page 35.
Table 20. Maximum bus length between terminators
Type of Interconnection Maximum Bus Length Between Terminators (in meters)
Point-to-point (1 server and 1 drive) 25
Multi-drop/daisy-chain (1 server and multiple
drives)
12 (LVD)
Note: The maximum bus lengths that are stated in this table include the internal length of the bus.
For maximum performance, multiple SCSI buses might be required (see “Multiple SCSI buses”), and IBM
Ultrium Tape Drives must be the only target devices that are active on the bus.
Note: Daisy-chaining is NOT recommended because of potential issues with SCSI bus performance, SCSI
cables/connectors, and host bus adapters.
Note: For maximum performance, the quantity of tape drives that you can attach to one SCSI bus is
limited, and is based on the type of bus that you have and the amount of data compression achieved.
Ultra160 SCSI buses have a bandwidth of 160 MB per second. The table lists the types of SCSI buses and
gives the recommended maximum quantity of drives that you can attach.
Table 21. Recommended maximum quantity of drives per SCSI bus
Type of Drive Ultra 160 SCSI Bus
LVD Ultrium 3 1 drive at 2:1 compression
Multiple SCSI buses
The library has two SCSI connectors for each tape drive in the library. Each drive can be daisy-chained
with a SCSI bus jumper.
Note: Daisy-chaining is NOT recommended because of potential issues with SCSI bus performance, SCSI
cables/connectors, and host bus adapters.
34 IBM TS3100 Tape Library and TS3200 Tape Library: Setup, Operator, and Service Guide Machine Type 3573
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