Data compression method and structure for a direct access storage device
First Claim
1. A method for storing compressed data in a direct access storage device (DASD) of the type including a fixed block architecture comprising the steps of:
- segmenting the DASD into a plurality of compression groups;
each of said compression groups having a fixed logical size;
allocating at least one compressed data region and an exception region within each compression group;
writing and reading related compressed data to and from said at least one compressed data region of one of said plurality of compression groups;
writing and reading compressed data exceptions to and from said exception region;
said compressed data exceptions including updated compressed data which exceeds an original storage space for corresponding original compressed data; and
writing a corresponding directory table within said exception region for each of said compression groups.
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Accused Products
Abstract
A data compression method and compression data structure are provided for a direct access storage device (DASD). The DASD is segmented into a plurality of compression groups. Each of the compression groups has a fixed logical size. A directory table is written within each of the compression groups. Each compression group has at least one compressed data region on which compressed data can be written and an exception region on which compressed data exceptions can be written. The compressed data exceptions include updated compressed data which exceeds an original storage space for corresponding original compressed data.
133 Citations
20 Claims
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1. A method for storing compressed data in a direct access storage device (DASD) of the type including a fixed block architecture comprising the steps of:
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segmenting the DASD into a plurality of compression groups;
each of said compression groups having a fixed logical size;allocating at least one compressed data region and an exception region within each compression group; writing and reading related compressed data to and from said at least one compressed data region of one of said plurality of compression groups; writing and reading compressed data exceptions to and from said exception region;
said compressed data exceptions including updated compressed data which exceeds an original storage space for corresponding original compressed data; andwriting a corresponding directory table within said exception region for each of said compression groups. - View Dependent Claims (2, 3, 4, 5, 6, 7, 13)
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8. A direct access storage device for storing a compression data structure, said compression data storage comprising:
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a plurality of compression groups;
each of said compression groups having a fixed logical size;a directory table written within each of said compression groups; each compression group having at least one compressed data region on which compressed data can be written; and each compression group having an exception region on which compressed data exceptions can be written;
said compressed data exceptions including updated compressed data which exceeds an original storage space for corresponding original compressed data. - View Dependent Claims (9, 10, 11, 12, 14, 15, 16)
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17. A system for reading and writing compressed data comprising:
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a host computer for providing and receiving data to a direct access storage device, said host computer including a direct access storage device storage management function and a logical directory for storing logical block addresses; a storage controller coupled to said host computer for receiving and compressing data and writing compressed data to the direct access storage device and for reading and decompressing compressed data from the direct access storage device and providing the data to said host computer; said direct access storage device including a plurality of compression groups;
each of said compression groups having a fixed logical size;a directory table written within each of said compression groups; each compression group having at least one compressed data region on which compressed data can be written; and each compression group having an exception region on which compressed data exceptions can be written;
each of said compressed data exceptions including updated compressed data which exceeds an original storage space for corresponding original compressed data. - View Dependent Claims (18, 19, 20)
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Specification