Method and means for managing DASD array accesses when operating in degraded mode
Patent 5265098 Issued on November 23, 1993. Estimated Expiration Date: 
November 23, 2010. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
November 23, 2010. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesSystem for recovering data stored in failed memory unit Parity spreading to enhance storage access Disk drive memory Disk drive memory Logical track write scheduling system for a parallel disk drive array data storage subsystem Failure-tolerant mass storage system Patent #: 5134619 InventorsApplicationNo. 562188 filed on 08/03/1990US Classes:714/6, Redundant stored data accessed (e.g., duplicated data, error correction coded data, or other parity-type data)714/710, Replacement of memory spare location, portion, or segment714/770Disk arrayExaminersPrimary: Beausoliel, Robert W. Jr.Assistant: Chung, Phung M. Attorney, Agent or FirmInternational ClassG06F 011/00AbstractA method and apparatus are disclosed which minimize the additional read and write loading for each remaining DASD in a DASD array occasioned by a single point of failure where subsets of DASDs may accessed asynchronously (RAID 4 or RAID 5). In this method, parity groups are written across the array in a pattern forming a balanced incomplete block design or the equivalent. In the event of failure of a DASD in the array, then any additional loading resulting from the failure is uniformly spread among the remaining DASDs.Other References
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