The IBM 3330 was a high-performance, high-capacity direct access storage subsystem for use with all IBM System/370 models as well as the IBM System/360 Model 195.
Each 3330 subsystem could have from two to 16 drives, giving users fast access up to 1.6 billion bytes of online storage. The subsystem could be attached to System/370 Models 135 though 168 via the IBM 3830 Storage Control Model 2 or to the Integrated Storage Control on the Model 145, 158 or 168 The Integrated Storage Control on Models 158 and 168 could attach two subsystems, each with up to 16 drives. A 3330 subsystem included standard checking and retry features that increased system reliability and availability for batch processing and data base applications.
Development of the 3330 -- known as 23XX, then 2314B and later Merlin during its pre-announcement life -- began in March 1965. Model 1 was rolled out in 1970 and first shipped the following year. The second model was introduced in 1972 and first delivered in 1974. A Model 11 was announced in 1973, with first customer shipments scheduled for March 1974.
According to some analysts, the Merlin drive had two notable innovations: the track-following servo system and the voice-coil actuator (similar to the element used to vibrate a loudspeaker diaphragm). "Merlin was the first disk storage product to use a voice-coil actuator under control of a track-following servo system. This combination provided better response time, higher track density, and more reliable operation than previously attainable."*
The Model 11 used a new 3336 Disk Pack with 200 million bytes of information, twice the capacity of the earlier model. It used a new feature that enabled the drives to operate independently during "erase" operations, permitting the data channel and control unit to serve other input/output devices. Previously-installed two-drive 3330s could be field converted to Model 11s.
The Model 11s were available at announcement under an extended term plan, which provided for a two-year contract period, at rental prices ranging from $1,550 to $1,850 a month. Purchase prices ranged from $74,000 to $87,000.
The 3330 was manufactured at IBM's General Products Division facilities in San Jose, California, where it was developed.
*Emerson W. Pugh, Lyle R. Johnson and John H. Palmer. IBM's 360 And Early 370 Systems. (Cambridge, Mass.: The MIT Press, 1991), p. 496.