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C-30 Compaq StorageWorks SSL2000 Series Library Maintenance and Service Guide
SCSI Interface Connectors
The Library is equipped with a Low Voltage Differential/Single-Ended (LVD/SE) SCSI
interface.
NOTE: If your Library is used on a single-ended SCSI bus, the internal wiring length of any rackmounted
SCSI system can approach the maximum length specification of a single-ended SCSI bus. You must
locate the storage cabinet close to the host computer to avoid excessive bus length. It is also especially
important in single-ended systems to use the highest quality SCSI cables. Bus errors caused by
excessive length or poor quality cables can significantly degrade performance and reliability.
NOTE: For those two-drive applications where both AIT drives run in SCSI-SE mode (rather than LVD
mode), each drive must be connected to its own SCSI bus.
Each drive is wired to an independent bus, with a pair of SCSI connectors. Drive 0 shares a
SCSI bus with the Library's robotics. To fully use the bus bandwidth, connect all the SCSI
buses together as shown in Figure C-31. The insets in Figure C-31 show how to connect the
SCSI cable, the jumper cables, and the terminator for one or two-drive units.
Each of the drives in the Library and the robotics is a separate SCSI device. When any two or
more devices are connected to the same SCSI bus, each separate SCSI device must be assigned
a unique SCSI address. For information on assigning SCSI addresses, see "Configuration," later
in this appendix.
To connect a Library to a host computer, the host must have at least one Wide SCSI controller
and the appropriate driver software. The controller must be LVD/SE or differential, as required
to match the unit interface.
Interface Cable Specifications
The Library is a high-performance system. To avoid degradation of performance, use the
highest-quality interface cables from a reputable manufacturer of computer cables. All SCSI
cables used with the Library should meet the following requirements:
Shielded or double-shielded, as required to meet EMI specifications
Impedance match with cable terminators that meet current SCSI specifications
Characteristic impedance between 115 and 160 ohms for differential
34-pair twisted-pair
Each end of a twisted pair ground connected to chassis ground
Maximum cable length of 10 ft (3 m) for a single-ended Fast/Wide SCSI bus, including
the internal wiring of SCSI device
Maximum cable length of 82 ft (25 m) for a differential Fast-Wide SCSI bus, including
the internal wiring of SCSI device
Maximum cable length of 39 ft (12 m) for an LVD SCSI bus
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