Data file directory system and method for writing data file directory information

• US 5,537,652 A
• Filed: 08/20/1990
• Issued: 07/16/1996
• Est. Priority Date: 08/20/1990
• Status: Expired due to Term

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Rolfe, Randy K., Friedl, Theodore J., Loen, Larry W., Gregg, Leon E.
• Primary Examiner(s): Elmore, Reba I.
• Application Number:
  US07/569,954
• Time in Patent Office: 2,157 Days
• Field of Search: 364/200 MS File, 364/900 MS File, 395/400, 395/425
• US Class Current: 711/111
• CPC Class Codes: G06F 11/08 Error detection or correction by redundancy in data representation, e.g. by using checking codes
• CPC Class Codes: G11B 20/1883 Methods for assignment of alternate areas for defective areas
• CPC Class Codes: G11B 2220/20 Disc-shaped record carriers
• CPC Class Codes: G11C 29/88 with partially good memories

Abstract

A data storage medium having the ability to recover from media errors includes a directory located at any desired region of a data storage area with redundant directory pointers at reserved locations. A unique file token is included in the directory entry for each data file and is also included in each extent list where the locations of parts of a fragmented data file are stored. Multiple extent lists are chained in two directions to facilitate reconstruction of the chain if part of the pointer information is lost.

Claims

1. A directory system for data files stored on a data storage medium on which data is written and from which data is read by a read/write means under the control of processor means, said directory system comprising:

means for writing a directory table at a selected location in a data storage area on the medium;

said data storage area including numerous defined segments on which blocks of data can be written;

means for defining an address for each defined segment;

means for writing a fragmented data file including blocks of data disposed at discontinuous segments of said data storage area;

means responsive to said fragmented data file writing means for writing a directory entry in said directory table for said data file, said directory entry containing information about said file, including a unique file identifier and including a pointer pointing to a selected list location in said data storage area for a list;

means responsive to said directory entry writing means for writing said list at said selected list location in said data storage area on the medium containing addresses of said written segments of said fragmented data file;

said unique file identifier being included in said list; and

means for writing a plurality of directory pointers on the medium each containing a directory list pointer to the address of said directory table.

2. A directory system for data files as claimed in claim 1 further comprising means responsive to a predetermined number of addresses of said data segments being written by said list writing means for writing at least one additional list on the medium containing addresses of additional segments of said fragmented data file, each said additional list including said unique file identifier.

3. A directory system for data files as claimed in claim 2 further comprising means for chaining said lists.

4. A directory system for data files as claimed in claim 3, wherein said chaining means include means for writing list pointers in each of said lists pointing to a next of said lists.

5. A directory system for data files as claimed in claim 3, said chaining means include means for writing list pointers in at least some of said lists pointing to a next of said lists and pointing to a prior of said lists.

6. A directory system for data files as claimed in claim 1 further comprising a reserved area on the medium from which blocks of data of said data file are excluded, and wherein said directory pointers writing means being controlled for writing said directory pointers on said reserved area.

7. Apparatus for writing data file directory information on a storage medium having a plurality of discrete locations defined in the storage medium and each of said discrete locations having an address, and said discrete locations including data storage locations available for data files and reserved system locations unavailable for data file storage, said apparatus comprising:

means for writing a file directory at a selected at least one of said data storage locations on the medium, said file directory containing an identification of and information about the addresses of data files in the data storage locations; and

means for writing a pointer at least at two different ones of said reserved system locations, said pointers pointing to the address of a data storage location where said filed directory is stored.

8. A method of arranging and finding data file directory information on a data storage medium on which data is written and from which data is read by a read/write means under the control of processor means, said data storage medium having a processor addressed data storage area and predetermined reserved regions, said method comprising the steps of:

storing a file directory at a selected location within the data storage area of the medium;

writing a pointer in at least two predetermined reserved regions separate from the data storage area of said medium pointing to the address of the location selected for the file directory;

said directory pointer being used for finding the file directory by reading the pointer from one of said reserved regions.