EP0552580A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Data storage method and apparatus for DASD arrays
Assignee: International Business Machines Corp
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Filing: 1992-12-10
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Granted: —
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Expires: 2012-12-10
Abstract
Abstract In a data storage method for checksum DASD arrays, files are classified by length and/or other characteristic. Each relatively shorter file is written to an address or contiguous addresses typically on a single DASD of the array. The checksum stored on a checksum DASD is updated by reading the existing checksum, XORing that with the new data and writing the new checksum. Each relatively longer file is subdivided into portions all of the same size, and the number of equal portions is equal to the number of data DASDs where the file is to be written. The portions are interleaved in a stripe of addresses on the data DASDs, and the checksum of the portions is written to the checksum DASD. The characteristic transition length is dynamically varied in order that each interleaved file is provided with contiguous addresses matched to the file size.
Inventors
- 👤 David A. Styczinski
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 10:47
CPC Classifications
G; G06; G06F; G06F11/00; G06F11/07; G06F11/08; G06F11/10; G06F11/1076; G06F11/1008; G06F3/00; G06F3/06; G06F3/0601; G11; G11B; G11B20/00; G11B20/10; G11B20/18; G11B20/1833; G06F3/0668; G06F3/0671; G06F3/0673
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
182 words
A method for storing data files in a data processing system having a storage array including a number of data DASD's each having physical addresses of locations where data is written and read, said method comprising the steps of: (a) separating data files to be stored into two different classes depending upon at least the criterion of file length; (b) writing data files from the class of relatively shorter files at addresses upon one of the number of DASD's; and (c) storing data files from the class of relatively longer data files by: (1) subdividing each data file from the class of relatively longer files into a number of portions equal to the number of data DASD's; (2) defining for each data file from the class of relatively longer files a file specific interleave depth uniform across all the data DASDs by assigning a stripe of matching physical addresses on each data DASD, the physical addresses of each data DASD being sufficient to receive one of the subdivided portions; and (3) writing the subdivided portions to the stripe of matching physical addresses.
Claim 2
Dependent Claim
31 words
A method as claimed in claim 1 wherein said step of writing the subdivided portions to the stripe of matching physical addresses is performed by writing all of said portions simultaneously.
Claim 3
Dependent Claim
33 words
A method as claimed in claim 1 wherein said subdividing step includes splitting the data file into a number of data blocks equal to an integer multiplied by the number of data DASDs.
Claim 4
Dependent Claim
25 words
A method as claimed in claim 1 wherein said defining step includes assigning said integer number of contiguous data block addresses of each data DASD.
Claim 5
Dependent Claim
28 words
A method as claimed in claim 1 wherein said separating step includes use of at least one additional criterion relating to the expected future use of the file.
Claim 6
Dependent Claim
46 words
A method as claimed in claim 1 further comprising reserving a supply of physical addresses in the storage array for use exclusively for storage of data files from the class of relatively longer data files, and said defining step includes assigning addresses from the reserved supply.
Claim 7
Dependent Claim
25 words
A method as claimed in claim 6 wherein said reserving step includes dedicating groups of sequential physical addresses in each DASD to the reserved supply.
Claim 8
Dependent Claim
28 words
A method as claimed in claim 1 further including maintaining for each file checksum data in a location different from the data DASDs where that file is written.
Claim 9
Dependent Claim
16 words
A method as claimed in claim 8 wherein said different location is a dedicated checksum DASD.
Claim 10
Dependent Claim
53 words
A method as claimed in claim 8 wherein said step of maintaining checksum data for the class of relatively shorter files is performed by reading prior checksum data, calculating new checksum data from the data file being written and from the existing checksum data, and overwriting existing checksum data with new checksum data.
Claim 11
Dependent Claim
43 words
A method as claimed in claim 8 wherein said step of maintaining checksum data for the class of relatively longer files is performed by calculating new checksum data from the data file being written and overwriting existing checksum data with new checksum data.
Claim 12
Dependent Claim
21 words
A method as claimed in claim 1 wherein said subdividing step includes forming portions each having a single data block address.
Claim 13
Dependent Claim
26 words
A method as claimed in claim 1 wherein said subdividing step includes forming portions each having an equal number of more than one data block addresses.
Claim 14
Dependent Claim
65 words
A data file storage apparatus comprising: an array of X data storage DASD devices, where X is a positive integer greater than one; means for allocating a stripe of M matching data block addresses on each of said X DASD devices to a data file, where M is a positive integer number of data block addresses; and means for dynamically varying the value of M.
Claim 15
Dependent Claim
17 words
The data file storage apparatus of claim 14 where said M matching data block addresses are contiguous.
Claim 16
Dependent Claim
59 words
The data file storage apparatus of claim 14 wherein said array includes N DASD devices where N is an integer greater than X, at least one of said N DASD devices being a checksum DASD; and means for maintaining checksum data for said stripe of M data block addresses on M matching data block addresses of said checksum DASD.
Claim 17
Dependent Claim
27 words
The data file storage apparatus of claim 14 wherein said means for dynamically varying the value of M is responsive to the size of the data file.
Claim 18
Dependent Claim
66 words
The data file storage apparatus of claim 17 wherein said means for dynamically varying the value of M comprises means for dividing a data file having an arbitrary length of L data block addresses into X equal segments, and said means for allocating comprises means for writing said data file to a stripe of L/X matching data block addresses on each of said X DASD devices.
Claim 19
Dependent Claim
142 words
A data storage system for use with a data processing system, said data storage system comprising: a plurality of data DASD devices each having physical addresses of locations where data is written and read; file classifying means for dividing data files into a first group of relatively smaller files and a second group of relatively larger files; means for subdividing files of the second group into a number of portions equal to the number of data DASD devices; means for assigning contiguous physical addresses on one data DASD to each file of said first group; and means for allocating to each file of said second group a stripe of contiguous and matching physical addresses on all of said data DASD devices, said stripe having on each data DASD a number of physical addresses matching in size each subdivided portion of the file.
References Cited (Backward Citations)
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