Technical data

• Data unit — This rackmount module contains a 16-cartridge magazine
to provide additional capacity in a multi-module configuration. The data
unit robotics works in conjunction with the robotics of the expansion unit
and base units. It is under control of the expansion unit.
The data unit works with either the TL881 or TL891 base unit.
• Pass through mechanism — The pass-through mechanism is attached
to the back of the expansion unit and each of the other modules and
allows the transfer of tape cartridges between the various modules. It is
controlled by the expansion unit.
For each base or data unit added to a configuration, the pass-through
mechanism must be extended by 17.8 centimeters (7 inches), which is
the height of each module. A 17.8-centimeter (7-inch) gap may be left
between modules (providing there is sufficient space), but additional
pass-through mechanism extensions must be used.
8.12.1.3 TL881 and TL891 Rackmount Scalability
The rackmount version of the TL881 and TL891 MiniLibraries provides
a scalable tape library system that you can configure for maximum
performance, maximum capacity, or various combinations between the
extremes.
Either library uses DLT IV tape cartridges but can also use DLT III or DLT
IIIxt tape cartridges. Table 8–17 lists the capacity and performance of a
TL881 or TL891 MiniLibrary in configurations that are set up for either
maximum performance or maximum capacity.
Table 8–17: TL881 and TL891 MiniLibrary Performance and Capacity Comparison
TL881 MiniLibrary TL891 MiniLibrary
Configured
for
Maximum:
Number of
Base Units
ab
Number of
Data Units
c
Transfer
Rate
d
Storage
Capacity
e
Transfer
Rate
f
Storage
Capacity
g
Performance
50
15 MB/sec
(54 GB/hr)
1.32 TB (66
cartridges)
50 MB/sec
(180 GB/hr)
2.31 TB (66
cartridges)
Capacity
14
3 MB/sec
(10.8
GB/hr)
1.8 TB (90
cartridges)
10 MB/sec
(36 GB/hr)
3.15 TB (90
cartridges)
a
Using an expansion unit with a full 16-cartridge magazine.
b
Each base unit has a full 10-cartridge magazine and two tape drives.
c
Using a data unit with full 16-cartridge magazine.
d
Up to 1.5 MB/sec per drive.
e
Based on 20 GB/cartridge uncompressed. It can be up to 40 GB/cartridge compressed.
f
Up to 5 MB/sec per drive.
g
Based on 35 GB/cartridge uncompressed. It can be up to 70 GB/cartridge compressed.
By modifying the combinations of base units and data units, the performance
and total capacity can be adjusted to meet the customers’ needs.
8–60 Configuring a Shared SCSI Bus for Tape Drive Use