EP0519669A2
Expired / Lapsed
EP
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Encoding and rebuilding data for a DASD array
Assignee: International Business Machines Corp
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Filing: 1992-06-15
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Granted: —
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Expires: 2012-06-15
Abstract
Abstract An (M-1)xM data array can be rebuilt from an array of M DASDs when up to R DASDs fail, where M is a prime number, the data array being encoded to include zero XOR sums along traverses of slopes 0, 1, 2, ..., R-1, extended cyclically over the data array. The rebuilding includes calculating XOR-sums along the traversed paths of R slopes, cyclic and linear shifts and XOR operations, recovering the unavailable DASDs by means of iterative solution of a set of recursions, and finally writing the rebuilt array back to onto M recording paths inclusive of any spare paths.
Inventors
- 👤 Miguel Mario Blaum
- 👤 Ron Moshe Roth
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 08:24
CPC Classifications
H; H03; H03M; H03M13/00; H03M13/03; H03M13/05; H03M13/09; H03M13/098; G; G06; G06F; G06F11/00; G06F11/07; G06F11/08; G06F11/10; G06F11/1076; G06F11/1092; G11; G11B; G11B20/00; G11B20/10; G11B20/18; G11B20/1833; G11C; G11C29/00; G11C29/70; G11C29/88; H03M13/11; H03M13/29; H03M13/2906; H03M13/2918; H03M13/2921
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
93 words
A method for encoding data onto an array of M DASDs, comprising the steps of: (a) assigning N DASDs to data, and P DASDs to parity (N+P=M); and (b) parity block coding, striping, and writing M data elements at a time from an (M-1)xM data array to the M DASD array, said coding being executed on a traverse along lines of slopes 0, 1, 2, ... P-1 respectively extended cyclically over the array, the coding logically combining data array elements included within each traverse slope such that they sum to a predetermined value.
Claim 2
Dependent Claim
56 words
A method according to claim 1, wherein the coding and writing steps further include the steps of generating the data array across a two-dimensional distribution of DASDs, or along a first dimension formed from M DASDs and a second dimension formed from (M-1) predetermined recording extents on at least one track of each of M DASDs.
Claim 3
Dependent Claim
28 words
A method according to claim 1 or 2, wherein each of the M traverse lines of a given slope commences in the top row of the data array.
Claim 4
Independent Claim
48 words
A method according to any preceding claim, wherein a (M′-1)xM′ data array, where M′ is not a prime number, can be encoded by first expanding the data array to include additional columns of uniform data to yield an effective array of (M-1)xM, where M is a prime number.
Claim 5
Independent Claim
14 words
A method according to any preceding claim, wherein each traverse line exhibits even parity.
Claim 6
Independent Claim
82 words
A method of rebuilding data encoded using the method of any previous claim onto spare DASDs, responsive to R DASDs being unavailable (R ≦ P), comprising parity coding the array elements from the M-R available DASDs onto the spare DASDs, said coding being executed on a traverse along lines of slopes 0, 1, 2, ... R-1 respectively extended cyclically over the array, the coding logically combining data array elements included within each traverse slope such that they sum to a predetermined value.
Claim 7
Dependent Claim
121 words
A data processing system having a CPU (1, 3), an array of at least M = N data + P parity DASDs, and means (7) inter-coupling the CPU and the array for accessing selectable ones of the DASDs, said means including means for read and write accesses of M data elements striped over M DASDs, said inter-coupling means comprising means for parity block coding and writing M data elements from an (M-1)xM data array to the M DASD array, said coding being executed on a traverse along lines of slopes 0, 1, 2, ... P-1 respectively extended cyclically over the array, the coding logically combining data array elements included within each traverse slope such that they sum to a predetermined value.
Claim 8
Dependent Claim
20 words
The system according to claim 7, wherein said intercoupling means includes means for synchronously accessing said array of M DASDs.
Claim 9
Dependent Claim
87 words
A system for rebuilding data encoded using the system of claim 7 or 8 onto spare DASDs, wherein said means for parity coding the array elements from the M-R available DASDs onto the spare DASDs is responsive to R DASDs being unavailable (R ≦ P) to execute the coding on a traverse along lines of slopes 0, 1, 2, ... R-1 respectively extended cyclically over the array, the coding logically combining data array elements included within each traverse slope such that they sum to a predetermined value.
Claim 10
Dependent Claim
94 words
A recording system having M = N data + P parity parallel recording paths, and means for reading and writing across a subset at a time of said M paths, said system comprising means for parity block coding and writing M data elements from an (M-1)xM data array to the M paths, said coding being executed on a traverse along lines of slopes 0, 1, 2, ... P-1 respectively extended cyclically over the array, the coding logically combining data array elements included within each traverse slope such that they sum to a predetermined value.
References Cited (Backward Citations)
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