Performance measurements and operational characteristics of the Storage Tek ACS 4400 tape library with the Cray Y-MP EL

With over 5000 units sold, the Storage Tek Automated Cartridge System (ACS) 4400 tape library is currently the most popular large automated tape library. Based on 3480/90 tape technology, the library is used as the migration device ('nearline' storage) in high-performance mass storage systems. In its maximum configuration, one ACS 4400 tape library houses sixteen 3480/3490 tape drives and is capable of holding approximately 6000 cartridge tapes. The maximum storage capacity of one library using 3480 tapes is 1.2 TB and the advertised aggregate I/O rate is about 24 MB/s. This paper reports on an extensive set of tests designed to accurately assess the performance capabilities and operational characteristics of one STK ACS 4400 tape library holding approximately 5200 cartridge tapes and configured with eight 3480 tape drives. A Cray Y-MP EL2-256 was configured as its host machine. More than 40,000 tape jobs were run in a variety of conditions to gather data in the areas of channel speed characteristics, robotics motion, time taped mounts, and timed tape reads and writes.