Distributed directory method and structure for direct access storage device (DASD) data compression

• US 5,537,658 A
• Filed: 06/07/1995
• Issued: 07/16/1996
• Est. Priority Date: 06/07/1995
• Status: Expired due to Term

• Current Assignee: HGST Netherlands B.V. (Western Digital Corporation)
• Original Assignee: International Business Machines Corporation
• Inventors: Walk, Bruce M., Bakke, Brian E., Moertl, Daniel F.
• Primary Examiner(s): Kulik, Paul V.
• Application Number:
  US08/484,612
• Time in Patent Office: 405 Days
• Field of Search: 395/600, 395/888, 395/404, 395/497.01, 395/497.02, 364/715.02
• US Class Current: 710/68
• CPC Class Codes: G06F 2003/0697 device management, e.g. handlers, drivers, I/O schedulers
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G11B 20/00007 Time or data compression or expansion audio compression based on psychoacoustics G10L19/00; data processing for reproducing audio data at different playback speeds G10L21/04; video compression H04N19/00; data compression per se H03M7/30

Abstract

A distributed directory structure and method are provided for writing directory information for compressed data on a direct access storage device (DASD). DASD includes a plurality of compression groups for storing compressed data. A micro directory table is written within each of the compression groups for the corresponding compressed data in the compression group. Compressed data and a directory update are written with a single write operation. A macro directory table is written in one area of the DASD. The macro directory table includes directory information used for translating a logical address to a physical base address for each compression group. The micro directory table includes directory information used for translating a logical address for a requested data page to a physical page address and page length within the compression group.

Claims

1. A method for writing directory information for compressed data on a direct access storage device (DASD) comprising the steps of:

providing a plurality of compression groups for storing compressed data;

writing a micro directory table within each of said compression groups for providing corresponding directory information for a corresponding compression group;

writing a macro directory table at a predefined location on the DASD for providing directory information for said plurality of compression groups; and

writing compressed data and a micro directory table updates with a single write operation.

2. A method for writing directory information as recited in claim 1 wherein said step of writing a directory table within each of said compression groups includes the step of storing a corresponding micro directory table for a corresponding one of said compression groups to provide compressed data page directory information for a data region contained within said corresponding compression group.

3. A method for writing directory information as recited in claim 1 wherein said step of writing a directory table within each of said compression groups includes the step of writing one directory page entry for each compression data page, said directory page entry including a page length and a page offset.

4. A method for writing directory information as recited in claim 1 wherein said step of writing a macro directory table at a predefined location on the DASD for providing directory information for said plurality of compression group includes the step of writing address translation information for translating a host logical block address to a compression group base address.

5. A method for writing directory information as recited in claim 4 wherein said step of writing a directory table within each of said compression groups includes the step of writing page translation directory information for identifying a page offset and a page length for a requested page from said compression group base address.

6. A distributed directory structure for directory information for compressed data on a direct access storage device (DASD) including a plurality of compression groups for storing compressed data, said distributed directory structure comprising:

a micro directory table located within a corresponding one of said compression groups, said micro directory table providing directory information for said corresponding compression group;

a macro directory table at a predefined location on the DASD, said macro directory table providing directory information for said plurality of compression group; and

means for writing compressed data and a micro directory table updates with a single write operation.

7. A distributed directory structure for directory information as recited in claim 6 wherein said micro directory table includes a plurality of page entries.

8. A distributed directory structure for directory information as recited in claim 7 wherein each page entry includes a page size value and a page location value.

9. A distributed directory structure for directory information as recited in claim 6 wherein said micro directory table includes directory information for identifying a page offset of a requested page, said page offset is from a starting compression group base address.