UNIVAC FASTRAND

UNIVAC FASTRAND

FASTRAND was a magnetic drum mass storage system built by Sperry Rand Corporation for their UNIVAC 1100 series and 490/494 series computers.

A voice coil actuator moved a bar containing multiple single track recording heads, so these drums operated much like moving head disk drives with multiple disks. The heads "flew" on self-acting hydrodynamic air bearings. The drums had a plated magnetic recording film.

The Fastrands were very heavy (5,000 pounds) and large, approximately 6' long. They required special rigging and mounts to install. At the time of their introduction the storage capacity exceeded any other random access mass storage disk or drum.

There were three models of FASTRAND drives:

• FASTRAND I had a single drum. The large mass of the rotating drum caused gyroscopic activity in the unit, making it tend to spin on the computer room floor as the Earth rotated under it. Very few of these devices were delivered.
• FASTRAND II (the majority of units produced) had two counter-rotating drums to eliminate the gyroscopic instability. One actuator bar with heads was located between the drums.
• FASTRAND III, introduced in 1970, was physically identical to the FASTRAND II, but increased the recording density by 50%.