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Tuning Internal Disk Apparatus Operations

IP.com Disclosure Number: IPCOM000048689D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Christian, JH: AUTHOR [+4]

Abstract

Rotational position sensing (RPS) is used for locating sectors on a disk storage apparatus. In setting up a data transfer, the sector must be identified a predetermined time before it arrives under the sensing head of the disk apparatus. For a serial transfer of several blocks of data separated by relatively small interblock gaps, such sectors cannot be reset and set within the gap time. For serial transmissions, this poses no problem. Where the various blocks are transferred to diverse locations in a random-access memory, a plurality of memory locations must be predetermined before the transfer starts. Setting up the transfer can take a variable length of time depending upon the blocks transferred.

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Tuning Internal Disk Apparatus Operations

Rotational position sensing (RPS) is used for locating sectors on a disk storage apparatus. In setting up a data transfer, the sector must be identified a predetermined time before it arrives under the sensing head of the disk apparatus. For a serial transfer of several blocks of data separated by relatively small interblock gaps, such sectors cannot be reset and set within the gap time. For serial transmissions, this poses no problem. Where the various blocks are transferred to diverse locations in a random-access memory, a plurality of memory locations must be predetermined before the transfer starts. Setting up the transfer can take a variable length of time depending upon the blocks transferred. Hence, the amount of elapsed time permitted for presetting the transfer is varied in accordance with the number of blocks transferred such that minimal latency occurs before the first sector is sensed.

A storage subsystem includes a disk storage apparatus DASD (direct access storage device) which is accessed via DASD access control which includes a radial actuator (not shown). It is desired to transfer a plurality of blocks of data from DASD via the circuits to a random access memory, each block going to a different portion of the memory in a random manner. A multiple record request is received. The calculated sector address is equal to the record request sector as modified by the number of storage address registers (SARs) tha...