Method and apparatus for establishing and maintaining the status of membership sets used in mirrored read and write input/output without logging
First Claim
1. An apparatus for maintaining the status of redundant copies of data on mirrored disk drives in a mirrored storage system, each of the mirrored disk drives including a copy of data, comprising a current copy indicator associated with each of the redundant copies of data wherein the current copy indicator further comprises a first set of identifiers indicating when a copy on one of the mirrored disk drives is to be updated and a second set of identifiers indicating the state of each of the copies.
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Accused Products
Abstract
A method and apparatus that maintains in stable storage an identification of which copies in a mirrored disk system are currently up to date without requiring the use of a logging mechanism. The invention may include a plurality of mirrored disk drives and a processing unit for controlling the writing and reading of data units to and from mirrored disk drives, wherein the processing unit establishes and maintains cohort sets for each mirrored disk drive. The cohort set represents the status of copies of the data units stored on the mirrored disk drives and contains membership information for redundant copies of data units stored in the plurality of mirrored disk drives. The membership information comprises a data structure of 2n status bits for identifying which disks contain current copies of the data units, where n is the number of disks in the system, and wherein the first n bits are used to indicate an intention to update the membership information for the copies and the second n bits are used indicate a current state of the membership information. The data structure may further include log(n) additional bits for identifying each mirrored disk.
209 Citations
73 Claims
- 1. An apparatus for maintaining the status of redundant copies of data on mirrored disk drives in a mirrored storage system, each of the mirrored disk drives including a copy of data, comprising a current copy indicator associated with each of the redundant copies of data wherein the current copy indicator further comprises a first set of identifiers indicating when a copy on one of the mirrored disk drives is to be updated and a second set of identifiers indicating the state of each of the copies.
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5. A system of mirrored disk drives containing redundant copies of data units, the system comprising;
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a plurality of mirrored disk drives; and a processing unit, coupled to the mirrored disk drives, for controlling the writing and reading of data units to and from mirrored disk drives; and wherein the processing unit establishes and maintains cohort sets for each mirrored disk drive, the cohort set representing status of copies of the data units stored on the mirrored disk drives, the cohort sets containing membership information for redundant copies of data units stored in the plurality of mirrored disk drives, the membership information comprising a data structure of 2n status bits for identifying which disks contain current copies of the data units, where n is the number of disks in the system, wherein the first n bits indicate an intention to update the membership information for the copies and the second n bits indicate a current state of the membership information. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A method of maintaining the status of mirrored disk drives containing redundant copies of data, the method comprising the steps of:
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establishing a cohort set on each of the mirrored disk drive representing a status of the copies stored on the mirrored disk drives, the cohort set containing membership information for redundant copies of data units stored in the plurality of mirrored disk drives, the membership information comprising a data structure of 2n status bits for identifying which disks contain current copies of the data units, where n is the number of disks in the system, wherein the first n bits indicate an intention to update the membership information for the copies and the second n bits indicate a current state of the membership information; and updating the contents of the cohort sets when a disk drive failure has been detected to reflect unavailability of the copy of data on the failed disk drive. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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- 31. A metadata file structure stored on each of a plurality of mirrored disk drives containing redundant copies of data units, the metadata file structure comprising a first and second set of n identifiers, wherein n is the number of mirrored disk drives and each identifier represents a mirrored disk drive, the first set of n identifiers indicating disk drives to be updated and the second set of identifiers indicating what disk drives contain current copies.
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49. A program storage device, readable by a computer, tangibly embodying one or more programs of instructions executable by the computer to perform method steps for managing mirrored disk drives containing redundant copies of data, the method comprising the steps of:
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establishing a cohort set on each of the mirrored disk drives representing a status of the copies stored on the mirrored disk drives, the cohort set containing membership information for redundant copies of data units stored in the plurality of mirrored disk drives, the membership information comprising a data structure of 2n status bits for identifying which disks contain current copies of the data units, where n is the number of disks in the system, wherein the first n bits indicate an intention to update the membership information for the copies and the second n bits indicate a current state of the membership information; and updating the contents of the cohort sets when a disk drive failure has been detected to reflect unavailability of the copy of data on the failed disk drive. - View Dependent Claims (50, 51, 52, 53, 54, 55)
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56. A memory for storing data for managing mirrored disk drives containing redundant copies of data, comprising:
a data structure stored in a memory of each of the mirrored disk drives, each of the data structure including a first and second set of n identifiers, wherein n is the number of mirrored disk drives and each identifier represents a mirrored disk drive, the first set of n identifiers indicating disk drives to be updated and the second set of identifiers indicating what disk drives contain current copies. - View Dependent Claims (57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73)
Specification