Browse Prior Art Database

Record Multiplexing in Data Storage System

IP.com Disclosure Number: IPCOM000038935D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 59K

Publishing Venue

IBM

Related People

Fry, SM: AUTHOR [+2]

Abstract

A system is described for record multiplexing, especially adapted for use in a tape storage system, where data is to be transferred in blocks between a channel and storage devices under the control of a control unit which includes a buffer. The operational speed of the channel is greater than the speed of the storage device by a factor of at least twenty percent. The system operates to decrease the utilization time of the faster device, i.e., the channel. This is accomplished by controlling block transfers so that a transfer from the device to the channel begins only if the buffer contains sufficient blocks of data so that the total transfer can be completed by the faster operation of the channel before data within the buffer is exhausted.

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Record Multiplexing in Data Storage System

A system is described for record multiplexing, especially adapted for use in a tape storage system, where data is to be transferred in blocks between a channel and storage devices under the control of a control unit which includes a buffer. The operational speed of the channel is greater than the speed of the storage device by a factor of at least twenty percent. The system operates to decrease the utilization time of the faster device, i.e., the channel. This is accomplished by controlling block transfers so that a transfer from the device to the channel begins only if the buffer contains sufficient blocks of data so that the total transfer can be completed by the faster operation of the channel before data within the buffer is exhausted. By the same token, transfer from the channel to the device in blocks is permitted by the control unit only if the buffer has sufficient room, whereby the channel can completely unload the desired data before room in the buffer is exhausted. The figure shows the data flow path for one embodiment of the system. Channel transfer control 13 selects, via 19, a channel 5, requesting service, and signals channel/buffer control 10 to transfer a record over the channel bus 14 between the channel 5 and the data buffer 15.

The transfer may be in either direction. In parallel, device transfer control 12 selects, via 18, a device 17 and signals device/buffer control 11 to transfer a record over the device bus 16 between the device 17 and the data buffer 15. The transfer may be in either direction and proceeds at a rate which is fixed for each device. The instantaneous channel transfer rate is greater than the device transfer rate unless a) transfer is from a channel to the data buffer and the data buffer is full, in which case,

channel transfer can only proceed at the rate the

device empties the buffer, or b) transfer is to a channel from the data buffer and the data buffer is empty, in which case

channel transfer can only proceed at the rate the

device fills the buffer. The system controls the time of initiation of channel transfers such that c) conditions a) and b) do not occur, i.e., the maximum instantaneous channel transfer rate is

achieved, and d) a channel is not selected until transfer can

procee...