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IBM 1311 disk storage drive

IBM 1311 Disk Storage Drive (center)

IBM 1311 Disk Storage Drive (center)
IBM 1311 Disk Storage Drive (center)

The IBM 1311 Disk Storage Drive provided storage for 2 million characters. Developers of the 1311 engineered twice the recording density of the IBM 1301 Disk Storage Unit by reducing the space between the head and the disk by about a factor of two.

The 1311 used the IBM Disk Pack (later designated the IBM 1316 ), an interchangeable package containing six 14-inch-diameter disks in a four-inch stack, weighing 10 pounds (seen above in the man's left hand). Each disk surface contained 20 pie-shaped regions. Sectors were segments of track lying within a region, and were the smallest addressable unit, with a capacity of 100 characters. Average access time to any sector was 250 milliseconds, which could be reduced to 150 milliseconds with an optional direct-seek feature. The disks were rotated at 1500 rpm, tracks (50 to the inch) were recorded at up to 1025 bits per inch, and the usual head-to-surface spacing was 125 microinches. The ten recording surfaces provided in normal usage a storage capacity of 2 million characters, the equivalent of approximately 25,000 punched cards or a fifth of a reel of magnetic tape.

The first host mainframes for the 1311 were the IBM 1401 Data Processing System , 1440 Data Processing System , 1620 Data Processing System and 1710 Control System.

By offering some of the advantages of both tapes and disks at a relatively low rental, the IBM 1311 met a need for versatile storage and became a very influential product. In addition, some analysts believe that the removable disk pack not only led to a new phase of disk storage but signaled the passing of the punched card era.