EP0458554A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method and apparatus for formatting data on DASD arrays
Assignee: International Business Machines Corp
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Filing: 1991-05-20
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Granted: —
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Expires: 2011-05-20
Abstract
Abstract Described is a method and means for managing access to a logical track of KN blocks of which K are parity blocks. The KN blocks are distributed and stored in an array of N DASDs having K blocks per physical track per DASD. The array includes control means for securing synchronous access to selectable ones of the DASDs responsive to each access request. The method involves (a) formatting the blocks onto the array using a row major order modulus as the metric for balancing the data rate and concurrency (the number of DASDs bound per access) and (b) executing the random sequences of large and small access requests over array.
Inventors
- 👤 James Thomas Brady
- 👤 Ruth Enid Cintron
- 👤 Stephen Goldstein
- 👤 Jean Ho-Ming Wang Ju
- 👤 Jaishankar Moothedath Menon
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 15:33
CPC Classifications
G; G06; G06F; G06F11/00; G06F11/07; G06F11/08; G06F11/10; G06F11/1076; G06F3/00; G06F3/06; G06F11/1008; G06F3/0601; G11; G11B; G11B20/00; G11B20/10; G11B20/18; G11B20/1833; G06F3/0668; G06F3/0671; G06F3/0673
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
168 words
A method for adjusting the data rate and concurrency with respect to read and write accesses of at least one logical track having KN sequentially ordered blocks distributed and stored onto an array of N DASDs, each DASD including a cyclic track recording medium, each track having a storage capacity of K blocks, said array including control means for securing synchronous access to selectable ones of the N DASDs, comprising the steps of: (a) formatting the KN blocks onto N tracks of the N DASDs of the array in row major order K modulo M and in column major order K modulo MN, M being less than or equal to K; and (b) executing large and small access requests over the array such that each access involves a synchronous data exchange of b blocks at a time with ( b M ) counterpart DASDs such that (N-b) DASDs are concurrently available for binding to another access request, M being the metric for balancing the data rate and concurrency.
Claim 2
Independent Claim
158 words
A method for managing access to at least one logical track of KN blocks of which K are parity, said KN blocks being distributed and stored in an array of N DASDs, each DASD including a cyclic track recording medium, each track having a storage capacity of K blocks, said array including control means for securing synchronous access to selectable ones of the N DASDs, comprising the steps of: (a) formatting the KN blocks onto N tracks of counterpart N DASDs of the array in row major order K modulo M and in column major order K modulo MN, M lying in the closed integer interval (1,K); and (b) executing large and small access requests over the N DASD array whereby the minimum number X of blocks transferred to achieve the maximum data rate for a given M is (N-1)M and lies in the closed interval ((N-1, (N-1)K) whose end points are defined by M=1 and M=K respectively.
Claim 3
Dependent Claim
40 words
A method as claimed in claim 2, wherein said execution step responsive to at least N-1 independent read accesses distributed over N-1 counterpart DASDs further includes the step of copying the contents of the accessed blocks in a concurrent manner.
Claim 4
Dependent Claim
72 words
A method as claimed in claim 2 or claim 3, wherein said formatting step includes formatting the array with KN blocks in row major order K modulo M and column major order K modulo MN such that he tracks on the counterpart N-1 DASDs contain (N-1)K data blocks and such that the track of the Nth DASD contains K parity blocks, each parity block spanning N-1 data blocks in column major order.
Claim 5
Independent Claim
129 words
A method as claimed in any of claims 2 to 4, wherein responsive to an update access to at least one data block at array location (i,j), the execution step further includes the steps of (c) synchronously reading the current data block at array location (i,j) and the current parity block at location (N,j), where i and j lie in the respective closed integer intervals (1,N-1) and (1,K); (d) altering the contents of the data block read from location (i,j); (e) calculating a new parity block by XORing the current contents of the parity block read from location (N,j), and the current and altered contents of the data block read from location (i,j); and (f) synchronously writing the altered data block and the new parity block back in place.
Claim 6
Dependent Claim
66 words
A method as claimed in claim 5, wherein said array further includes a cache operably responsive to said control means, and wherein the execution step further includes the step of: (g) accessing said cache for a block array location (i,j), and, in the event said data blocks unavaiable in said cache, staging blocks to said cache at array locations (i,j) through (i,K) from the ith DASD.
Claim 7
Independent Claim
85 words
A method as claimed in any of claims 2 to 6, wherein K parity blocks associated with a first logical track of KN blocks being stored on a first track of the Nth DASD, and further wherein K parity blocks associated with a second logical track of KN blocks are stored on a first track of the (N-1)th DASD, and further wherein the K parity blocks associated with a third logical track of KN blocks are stored on a first track of the (N-2)th DASD.
Claim 8
Dependent Claim
38 words
A method as claimed in claim 2, wherein K parity blocks are distributed across N DASDs of the array K modulo M such that exactly M parity blocks are written to the counterpart physical track of each DASD.
Claim 9
Dependent Claim
36 words
A method as claimed in claim 1 or 2, wherein the number of sequentially ordered blocks is T*KN, T being the number of logical tracks, and further wherein M lies in the closed integer interval (1,TK).
Claim 10
Dependent Claim
115 words
A data processing system having a CPU, an array of N DASDs, and means intercoupling the CPU and the array for synchronously accessing selectable ones of the DASDs, said means including means for read and write accesses of KN sequentially ordered blocks distributed and stored onto said N DASDs, each DASD including a cyclic track recording medium, each track having a storage capacity of K blocks, wherein said means further comprises means for formatting the KN blocks onto N tracks of the N DASDs of the array in groups, each group comprising M sequential blocks where 1 < M ≦ K, with groups 1 to N being recorded sequentially on DASDs 1 to N respectively.
Claim 11
Dependent Claim
75 words
A system as claimed in claim 10, wherein said accessing means further comprises: (c) a cache for storing a predetermined mumber of blocks therein and responsive to access requests originating from the CPU for exchanging requested blocks with the CPU if available or to cause the request to passed to the DASDs; and (d) means for staging blocks to the cache from the requested block to the physical end of track on the counterpart DASD.
Claim 12
Independent Claim
82 words
A method for storing data on an array of N DASDs, each DASD including a recording medium in which said data is stored in tracks, each track having a storage capacity of K blocks, said method comprising: formatting K*N blocks of a logical track of data in N tracks of N corresponding DASDs in groups, each group comprising M sequential blocks where 1 < M ≦ K, with groups 1 to N 1 being recorded sequentially on DASDs 1 to N respectively.
References Cited (Backward Citations)
No citation records indexed.
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