Browse Prior Art Database

Overlapping Data Streaming and Concurrent Read Write References Within a Storage Subsystem

IP.com Disclosure Number: IPCOM000053189D
Original Publication Date: 1981-Sep-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Kinberg, C: AUTHOR [+2]

Abstract

The invention depicted in the figure is used to allow normal DASD (dire storage device) or tape operations to take place as usual and to allow completion of data backup/restore operations between DASD and tape without going through the system. While one DASD is participating in backup/restore, other DASDs can be simultaneously accessed via the optional path by the system.

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Overlapping Data Streaming and Concurrent Read Write References Within a Storage Subsystem

The invention depicted in the figure is used to allow normal DASD (dire storage device) or tape operations to take place as usual and to allow completion of data backup/restore operations between DASD and tape without going through the system. While one DASD is participating in backup/restore, other DASDs can be simultaneously accessed via the optional path by the system.

The Channel-Device Buffer is used to match the speed (data rate) of the channel with that of a device, DASD or tape, when data is transferred to/from the channel. The Backup/Restore Buffer is used to match speeds of DASD and tape for a backup/restore operation. Each microprocessor typically contains ROS (read-only storage) and RAM (random-access memory).

Although the subsystem can perform a backup/restore operation in either dedicated or concurrent system environment, the operation is described here in terms of the latter, which tends to make use of most or all subsystem components at one time. While data to be backed up or restored flows between one DASD and a tape unit through the Backup/ Restore Buffer, an independent data path between another DASD and the channel through a separate optional DASD Interface Adapter may be active, using the Channel-Device Buffer (see figure). This option allows simultaneous accessing of DASDs not involved in the ongoing backup/restore operation.

All commands issued by the system to the subsystem are intercepted by the Main Microprocessor, which, after decoding them and fetching associated parameters, builds control block(s) in a common area accessible to both Main and Backup/Restore microprocessors (MPs). For control...