Client Direct Scsi Operation; Scsi Hvd Or Lvd Considerations; Scsi Cable Restrictions; Table 1-3. Scsi Cable Restrictions - StorageTek L700 Service Manual

Client Direct SCSI Operation

Client Direct SCSI Operation
For client direct connection, a SCSI host is connected to the tape library and drives. The
drives may share the same SCSI bus as the library (termed "on bus") or operate on their
separate SCSI bus (termed "off bus").
The connection from the client to the tape library and/or drives is a SCSI Type-3 68-pin
cable. This cable may be a unique channel from the host or it may be daisy-chained to a
shared data bus with the tape library or one or more drives.

SCSI HVD or LVD Considerations

With the advent of Ultrium tape drives, customers now have choices as to the type of
SCSI interface on which they wish to operate: High Voltage Differential (HVD) or Low
Voltage Differential (LVD). As shown in
cable lengths but throughput is lower than LVD; the LVD interface restricts cable
lengths, but provides faster throughput.
As a service representative you must understand these cabling requirements as well as:
• How LVD Ultrium drives are different internally from HVD Ultrium drives
• How the library (that is, the control path) is converted to LVD operation
• What the Host Bus Adapter (HBA) requirements are
• What the consequences for mixing SCSI types on a bus are.

SCSI Cable Restrictions

The library and drives support only SCSI Type-3 connectors. If you use SCSI Type-1 or -2
connectors, you must use a SCSI Type-1- or SCSI Type-2-to-SCSI Type-3 adapter.
Note: If you are connecting the library or drives to an LVD SCSI bus, the cable can be
Table 1-3

Table 1-3. SCSI Cable Restrictions

Application
Single-Ended
(Library only)
High Voltage
Differential
Low Voltage
Differential
A-8
no longer than 12 m (39.4 ft).
lists additional restrictions for SCSI connections that you should keep in mind.
Length Restriction
Stub length: 0.1 m (4 in.)
5 to 10 Mb data transfer rate: 3 m (10 ft)
1 to 5 Mb data transfer rate: 6 m (20 ft)
Stub length: 0.2 m (10 in.)
1 to 10 Mb data transfer rate: 25 m (82 ft)
Stub length: 0.1 m (3.9 in.)
108 GB data transfer rate: 12 m (39.37 ft)
Fourteenth Edition
StorageTek Proprietary
Table 1-3, the HVD interface allows longer
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