IBM 3850

The IBM 3850 Mass Storage System was an online tape library used to hold large amounts of infrequently accessed data. It was one of the earliest examples of nearline storage.

History

Starting in the late-1960s IBM's lab in Boulder, Colorado began development of a low-cost mass storage system based on magnetic tape cartridges. The tapes would be accessed automatically by a robot (known as an accessor) and fed into a reader/writer unit that could work on several tapes at the same time. Originally the system was going to be used as a directly attached memory device, but as the speed of computers grew in relation to the storage, the product was re-purposed as an automated system that would offload little-used data from hard disk systems. Known internally as Comanche while under development, IBM management found a number of niche uses for the concept, and announced it officially as the IBM 3850 on October 9th, 1974.

Description

The MSS (as it was known) consisted of a library of cylindrical plastic cartridges, two inches wide and 4 inches (100 mm) long, each holding a spool of tape 770 inches (20 m) long storing 50MB. These cartridges were held in a hexagonal array of bins in the IBM 3851 Mass Storage Facility. New cartridges were rolled into the facility and were automatically stored in a vacant bin. The data was accessed via one or two IBM 3330 disk drives, the data being transferred automatically between cartridge and disk drive in processes called staging and destaging. These were all connected together with the IBM 3830 Storage Control (also used for disk storage alone), the entire system making up a 3850 unit.