Technical data

Appendix B of the TL81X/TL894 Automated Tape Library
for DLT Cartridges Facilities Planning and Installation Guide
provides figures showing various bus configurations. In these
figures, the configuration changes have been made by removing
the terminators from both drives, installing the SCSI bus jumper
cable on the drive connectors vacated by the terminators, then
installing an HD68 SCSI bus terminator on the SCSI bus port
connector on the cabinet exterior.
Doing this is not wrong, but by reconfiguring in this manner, the
length of the SCSI bus is increased by 1.5 meters (4.9 feet), and
may cause problems if SCSI bus length is of concern.
8.9.4 Connecting the TL894 Tape Library to the Shared SCSI Bus
The TL894 tape libraries have up to 3 meters (9.8 feet) of internal SCSI
cabling per SCSI bus. Because of the internal SCSI cable lengths, you
cannot use a trilink connector or Y cable to terminate the SCSI bus external
to the library as is done with other devices on the shared SCSI bus. Each
SCSI bus must be terminated internal to the tape library, at the tape drive
itself with the installed SCSI terminators. Therefore, TruCluster Server
clusters using the TL894 tape library must ensure that the tape library is
on the end of the shared SCSI bus.
In a TruCluster Server cluster with a TL894 tape library, the member
systems and StorageWorks enclosures or RAID subsystems may be isolated
from the shared SCSI bus because they use trilink connectors or Y cables.
However, the ASE must be shut down to remove a tape loader from the
shared bus.
Figure 8–13 shows a sample TruCluster Server cluster using a TL894 tape
library. In the sample configuration, the tape library has been connected in
the two-bus mode by jumpering tape drive 0 to tape drive 1 and tape drive
2 to tape drive 3 (see Section 8.9.3 and Figure 8–12). The two SCSI buses
are left at the default SCSI IDs and terminated at drives 1 and 3 with the
installed terminators (part number 0415619).
To add a TL894 to a shared SCSI bus, select the member system or storage
device that will be the next to last device on the shared SCSI bus. Connect a
BN21K or BN21L cable between the Y cable on that device to the appropriate
tape library port.
8–42 Configuring a Shared SCSI Bus for Tape Drive Use