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Patent Agency Ranking
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公开(公告)号：DE69504918T2
公开(公告)日：1999-05-27
申请号：DE69504918
申请日：1995-06-16
Applicant: IBM
Inventor： CHEN JAMES C , GLIDER JOSEPH S , SHIPMAN LLOYD R , STAMNESS JESSE I
Abstract: The present system may be utilized to minimize access performance penalties in memory subsystems which utilize redundant arrays of disk memory devices. Redundant arrays of disk memory devices provide levels of reliability which are not available with single storage devices; however, the redundancy carries with it an access performance degradation due to the requirement that such systems write data segments and parity elements to the array each time an application updates data within the system. A large nonvolatile cache is therefore provided in association with a redundant array of disk memory devices. Each time a data segment is written or read the data segment is staged from the array to the nonvolatile cache, if the data segment is not already within the cache. Additionally, if the operation is an update, a parity element associated with the data segment to be updated is also staged to the cache with the existing data segment content. An updated parity element is then calculated based upon the updated data, the existing data and the existing parity element. Data segments and associated parity elements are then maintained in the cache for future reading and updates until the number of updated data segments within the cache exceeds a predetermined value. Thereafter, selected data segments and associated parity elements are destaged from the cache to the array based upon a "Least Recently Utilized" (LRU) or "minimum seek" algorithm.
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公开(公告)号：DE69504918D1
公开(公告)日：1998-10-29
申请号：DE69504918
申请日：1995-06-16
Applicant: IBM
Inventor： CHEN JAMES C , GLIDER JOSEPH S , SHIPMAN LLOYD R , STAMNESS JESSE I
Abstract: The present system may be utilized to minimize access performance penalties in memory subsystems which utilize redundant arrays of disk memory devices. Redundant arrays of disk memory devices provide levels of reliability which are not available with single storage devices; however, the redundancy carries with it an access performance degradation due to the requirement that such systems write data segments and parity elements to the array each time an application updates data within the system. A large nonvolatile cache is therefore provided in association with a redundant array of disk memory devices. Each time a data segment is written or read the data segment is staged from the array to the nonvolatile cache, if the data segment is not already within the cache. Additionally, if the operation is an update, a parity element associated with the data segment to be updated is also staged to the cache with the existing data segment content. An updated parity element is then calculated based upon the updated data, the existing data and the existing parity element. Data segments and associated parity elements are then maintained in the cache for future reading and updates until the number of updated data segments within the cache exceeds a predetermined value. Thereafter, selected data segments and associated parity elements are destaged from the cache to the array based upon a "Least Recently Utilized" (LRU) or "minimum seek" algorithm.
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公开(公告)号：CA1299757C
公开(公告)日：1992-04-28
申请号：CA570926
申请日：1988-06-30
Applicant: IBM
Inventor： BEARDSLEY BRENT C , HEFFERON EUGENE P , LYNCH KENNETH R , SHIPMAN LLOYD R
Abstract: A data processing system includes a plurality of host systems and peripheral subsystems, particularly data storage subsystems. Each of the data storage subsystems includes a plurality of control units attaching a plurality of data storage devices such as direct access storage devices (DASD) for storing data on behalf of the various host systems. Each of the control units have a separate storage path for accessing the peripheral data storage devices using dynamic pathing. The storage paths can be clustered into power clusters. Maintenance personnel acting through maintenance panels on either the control units or the peripheral data storage devices activate the subsystem to request reconfiguration of the subsystem from all of the host systems connected to the subsystem. The host systems can honor the request or reject it based upon diverse criteria. Upon each of the host systems approving the reconfiguration, the subsystem is reconfigured for maintenance purposes. Upon completion of the maintenance procedures, a second reconfiguration request is sent to the host systems for causing quiesce devices to resume normal operations. TU986011
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