FASTRAND was a magnetic drum mass storage system built by Sperry Rand for their UNIVAC 1100 series and other computers. Each subsystem included control units and up to eight FASTRAND units, with dual-access versions allowing simultaneous operations. The drums used a voice coil actuator moving multiple single-track heads on hydrodynamic air bearings, with an optional Fastband feature providing rapid access through fixed heads. Weighing around 5,000 pounds and nearly 8 feet long, they required special installation due to their size and weight. Three models existed: FASTRAND I, notable for gyroscopic precession; FASTRAND II with counter-rotating drums to eliminate this effect; and FASTRAND III, which increased recording density by 50%. At introduction, their storage capacity surpassed all other random access devices.
Specifications (FASTRAND II)
Storage capacity: 22,020,096 36-bit words = 132,120,576 6-bit FIELDATA characters = 99 megabytes (8-bit bytes) per device Drum rotation rate: 880 RPM (14.7 rotations per second) Heads: 64 Sector size: 28 36-bit words Track size: 64 sectors (1,792 36-bit words) Track density: 105 tracks per inch Average Access time (seek time plus rotational latency): 92 milliseconds Data transfer rate: 26,283 36-bit words per second = 118 kilobytes per second (8-bit bytes) on 1100 series machines Recording density, one-dimensional: 1,000 bits per inch (along one track) Recording density, two-dimensional: 105,000 bits per square inch of drum surface Max FASTRAND devices (drum units) per controller: 8 Controller price: $41,680 (1968 US dollars) FASTRAND device price: $134,400 (1968 dollars, equivalent to $1.22 million in 2024 dollars) Weight per FASTRAND device: 4,500 pounds Weight per kilobyte: 6 ounces (170 g)
Storage allocation
Despite the name, FASTRAND was slow. The head positioning time was significant, so software allocated storage by tracks (1,792 words, 10,752 characters or 8,064 eight-bit bytes) or "positions", a group of 64 tracks (114,688 words, 688,128 characters or 510,096 eight-bit bytes) which were under the heads at a single time. This storage allocation method remained on the 1100 series machines long after drums had been replaced by disks.
The track storage units were checkboarded so that, with precise computation of the program's processing time, one could create software with processing time per unit of Fastrand blocks that resulted in a program running in synchronism with the data transfer rate of the drum. Further, the track-to-track head movement time afforded an additional processing speed coordination possibility that permitted the computational rate to match the data transfer rate for large (for the time) data sets without being delayed by losing synchronism with the mass storage transfers.