The Computing Center has two 2 StorageTek Silos. One is a 4410, attached to our IBM 9672 Enterprise Server and the other, a 9310, is attached to our data management machine, a Sun E4500. They are basically identical with two exceptions. The silo attached to the IBM has two more tape drives, and it has two 40 slot CAP (export/input) doors. While the silo attached to the Sun system is has a faster robotic arm (350 tape exchanges per hour vs. 135 for the 4410). The tape drives in the IBM silo are attached via ESCON channels, while the tape drives in the other silo are attached via FW SCSI controllers.
The one primarily used by our Sun E4500. has six 9840A SCSI attached drives. (The 4 old tape drives are still available in this silo for use by the IBM system.) The 9840A drives, and tapes, allow for 20GBs uncompressed per tape (we typically see a 2:1 compression ratio), and 9MB/sec per drive transfer rates. This provides approximately 120 terabytes of storage in the silo capacity with no compression. With compression we can store nearly 300 terabytes of data in the silo! For comparison, with our old Timberline drives (3490 type) we could only store approximately 4.8 terabytes data (uncompressed) in the silo.
Tapes are stored in the silo, which is a 12 sided structure, along the outside and inner walls. A center mounted arm swings in a circle to position to the correct wall panel and slot. A vertical arm slides up and down to position the grabbers on the correct row.
Our combined upgrades gives the backup users and research community approximately 7 times the throughput of the old tape drives, and the capacity of nearly 25 times what we had with the originally installed equipment.