Browse Prior Art Database

Eliminating Data Interleaving in Two Head Per Arm Disk Files

IP.com Disclosure Number: IPCOM000084692D
Original Publication Date: 1975-Dec-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 37K

Publishing Venue

IBM

Related People

Gold, DE: AUTHOR

Abstract

A method/apparatus is described for avoiding interleaving of logic record elements distributed on disparate tracks of a disk storage system and read by a two read/write head accessing mechanism. The accessing mechanism is mounted on a common arm on opposite sides of the rotation access of the disk where such partitioned logical record has been recorded on the disparate physical tracks at constant bit density, where all of the logical tracks have a constant length, as shown in U. S. Patent 3,831,191.

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Eliminating Data Interleaving in Two Head Per Arm Disk Files

A method/apparatus is described for avoiding interleaving of logic record elements distributed on disparate tracks of a disk storage system and read by a two read/write head accessing mechanism.

The accessing mechanism is mounted on a common arm on opposite sides of the rotation access of the disk where such partitioned logical record has been recorded on the disparate physical tracks at constant bit density, where all of the logical tracks have a constant length, as shown in U. S. Patent 3,831,191.

The method comprises the steps of linearly ordering the elements of the logical record into a buffer capable of being simultaneously filled or emptied from both ends. This is done by writing the data on the first physical track from the beginning in ascending order to the point of partition, and writing the data on the second physical track from the end to the point of partition in descending order.

Referring to the Fig. 1, there are shown two A-B buffers for either reading or writing. A control unit interacting through a switching arrangement (SW1, SW2, SW3) assists these functions by ping-ponging the two buffers. On reading the physical tracks, one buffer will be accumulating the data from the two buffers associated with the corresponding read/write heads. Switches SW2 and SW3 are set for providing the data path from that A-B buffer dedicated to reading.

When the enabled buffer is full, SW2 and SW3 enable the other A-B buffer and switch SW1 will switch to establish a data path for the buffer just filled. This process continues until the read request is satisfied. Switches SW2 and SW3 always function in parallel, while SW1 couples that buffer not linked through SW2 and SW3. A single control signal suffices for activating all of the switches.

The A-B buffer memory must be capable of being driven at a maximum gross data rate as a function of the recording density and the linear speed of the outermost track of the disk drive, and at a minimum data rate determined by the linear speed of the innermost track. Each A-B buffer memory is assumed, for the purpose of explanation, to be linearly ordered. A "beginning" and an "end" of each is referred to. Data are entered into a buffer from t...