Compressed common file directory for mass storage systems

• US 5,778,374 A
• Filed: 08/03/1995
• Issued: 07/07/1998
• Est. Priority Date: 08/03/1995
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Dang, Chi-Thanh, Dang, Chi-Hung
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): Corrielus, Jean M.
• Application Number:
  US08/510,995
• Time in Patent Office: 1,069 Days
• Field of Search: 395/601, 395/602, 395/610, 395/616, 395/621, 395/200.09, 395/898, 707/101, 707/200-206, 345/971, 364/715.02
• US Class Current: 1/1
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: Y10S 707/99942 Manipulating data structure, e.g. compression, compaction, compilation
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 715/971 Cooperative decision support systems for group of users

Abstract

A file management system for accessing mass storage systems, employing a compressed common file directory ("CCFD") that occupies a minimum amount of storage space. The CCFD is implemented in a storage system including a library of media, one or more storage drives that may be permanently or selectively coupled to the media, and a controller connected. Each piece of media includes a local file directory, which contains a listing of the files stored on that piece of media cross-referenced to those files'"'"' addresses on the media item. The controller contains or has convenient access to the CCFD. When access to a file is desired, the CCFD is used to quickly identify the piece of media containing that file. More particularly, the CCFD includes a first data structure including a list of encoded filenames cross-referenced to a list oil compressed media IDs. Each encoded filename comprises a filename of a file stored in one or more of the media, encoded with a selected encoding scheme. For each encoded filename, the associated compressed media ID comprises an encoded name of a piece of media containing that file. A second data structure includes a list of each compressed media ID cross-referenced to a media location identifier specifying the location of that media item in the library. To access a desired file stored in the library, the file'"'"'s name is first encoded. Then, the encoded filename is cross-referenced in the first data structure to obtain a compressed media ID. Using the second data structure, the compressed media ID is used to determine the media'"'"'s location identifier. The media location identifier is then used to locate the media containing the file. After the media is located and obtained, the media'"'"'s local file directory is searched to find the desired file'"'"'s address in that piece of media.

Claims

1. A compressed common file directory for use in a mass storage system that includes a plurality of physically separate media items, each media item being associated with a media ID and a media location identifier, said common file directory comprising:

a first data structure comprising a list of unique encoded filenames and a list of compressed media IDs, wherein each particular encoded filename comprises a filename of a particular file residing on at least one of the media items and encoded with a selected encoding scheme, and wherein each particular encoded filename is cross-referenced to a compressed media ID comprising a media ID encoded with a selected encoding scheme, said media ID uniquely identifying the particular media item containing the particular file; and

a second data structure including a list of all compressed media IDs, wherein each particular compressed media ID comprises a media ID of a particular item of the plurality of media items encoded with a selected encoding scheme, and wherein each particular compressed media ID is cross-referenced to a media location identifier indicating a location of the particular media item in the mass storage system.

2. The file directory of claim 1, wherein the first and second data structures are stored in a controller associated with the plurality of media items.

3. The file directory of claim 1, wherein the first and second data structures are stored on at least one of the plurality of media items.

4. The file directory of claim 3, wherein the first and second data structures are additionally stored in random access memory accessible by the controller.

5. The file directory of claim 1, wherein every one of the selected encoding schemes comprises cyclic redundancy coding.

6. The file directory of claim 1, wherein the first and second data structures comprise a single lookup table.

7. The file directory of claim 1, wherein the first and second data structures comprise two lookup tables.

8. The file directory of claim 1, wherein each media item contains a local file directory containing a list of files stored on that media item, where each file is cross-referenced to its memory address on that media item.

9. The file directory of claim 1, further comprising a buffer to store changes occurring to the first and second data structure.

10. The file directory of claim 1, further comprising a buffer to store changes occurring to the first and second data structure.

11. A file storage system, comprising:

a library housing containing a plurality of physically unattached media items;

a shared storage drive selectively connectable to the media items;

a controller coupled to the storage drive; and

a memory device, containing a compressed common file directory, comprising;

a first data structure comprising a list of unique encoded filenames and a list of compressed media IDs, wherein each particular encoded filename comprises a filename of a particular file residing on at least one of the media items and encoded with a selected encoding scheme, and wherein each particular encoded filename is cross-referenced to a compressed media ID comprising a media ID encoded with a selected encoding scheme, said media ID uniquely identifying the particular media item containing the particular file; and

a second data structure including a list of all compressed media IDs, wherein each particular compressed media ID comprises a media ID of a particular item of the plurality of media items encoded with a selected encoding scheme, and wherein each particular compressed media ID is cross-referenced to a media location identifier identifying a physical location of the particular media item with in the library.

12. The file storage system of claim 11, wherein the memory device comprises a magnetic data storage disks.

13. The file storage system of claim 11, wherein the memory device comprises a random access memory circuit.

14. The file storage system of claim 11, wherein the media items comprise optical packages.

15. The file storage system of claim 11, wherein the media items comprise magnetic data storage disks.

16. A file storage system, comprising:

a housing containing a plurality of separately movable media items;

a plurality of storage drives each coupled to at least one of the media items;

a controller coupled to the storage drive; and

a memory device, containing a compressed common file directory, comprising;

a first data structure comprising a list of unique encoded filenames and a list of compressed media IDs, wherein each particular encoded filename comprises a filename of a particular file residing on at least one of the media items and encoded with a selected encoding scheme, and wherein each particular encoded filename is cross-referenced to a compressed media ID comprising a media ID encoded with a selected encoding scheme, said media ID uniquely identifying the particular media item containing the particular file; and

a second data structure including a list of all compressed media IDs, wherein each particular compressed media ID comprises a media ID of a particular item of the plurality of media items encoded with a selected encoding scheme, and wherein each particular compressed media ID is cross-referenced to a media location identifier indicating a physical location of the particular media item within the housing.

17. The file storage system of claim 16, further including a buffer to store changes occurring to the compressed common file directory.

18. The file storage system of claim 16, wherein the memory device comprises a magnetic data storage disks.

19. The file storage system of claim 16, wherein the memory device comprises a random access memory circuit.

20. The file storage system of claim 16, wherein the media items comprise optical packages.

21. The file storage system of claim 16, wherein the media items comprise magnetic data storage disks.

22. A method of accessing files contained in a mass storage system that includes a plurality of physically separate media items arranged in a library, each media item having a physical location within the library uniquely identified by a media location identifier, wherein the media items contain multiple files each file associated with a unique filename, said method comprising the steps of:

receiving a request for access to a desired file, at least part of which resides on a first one of the media items;

encoding the desired file'"'"'s filename with a predetermined encoding scheme to provide a first encoded filename;

cross-referencing the first encoded filename in a data structure to obtain a first media location identifier corresponding to the first media item, said cross-referencing step including;

cross-referencing the first encoded filename in a first data structure to obtain a first compressed media ID corresponding to the first media item, wherein said first compressed media ID comprises an abbreviated code uniquely identifying the first media item; and

cross-referencing the compressed media ID in a second data structure to obtain a first media location identifier corresponding to the first media item, said media location identifier indications a physical position of the first media item in the library;

using the first media location identifier to locate the first media item in the library, and coupling the first media item to a storage drive;

reading a first local file directory contained on the first media item to identify an address at which the desired file resides on the first media item; and

reading the desired file by reading data beginning from the address of the first media item.

23. The method of claim 22, wherein each compressed media ID comprises an encoding of a media ID uniquely identifying the first media item.

24. The method of claim 23, wherein the encoding of media IDs comprises cyclic redundancy coding.

25. The method of claim 22, wherein the encoding step comprises the steps of applying cyclic redundancy coding to the filename.

26. The method of claim 22, wherein the request includes the desired file'"'"'s filename.

27. The method of claim 22, wherein the first data structure comprises a listing of encoded filenames each linked to a corresponding compressed media ID that comprises an abbreviated code uniquely identifying media items where files identified by the filenames reside.

28. The method of claim 22, wherein the second data structure comprises a listing of compressed media IDs linked to corresponding media location identifiers.

29. The method of claim 22, further comprising the steps of changing the data structure in response to changes in storage of the files of the mass storage system.

30. The method of claim 29, wherein the changes include deletion of a file.

31. The method of claim 29, wherein the changes include addition of a file.

32. The method of claim 22, further comprising the steps of:

generating and storing updates to the data structure to reflect changes in storage of the files of the mass storage system; and

at selected times revising the data structure to reflect the stored updates.

33. The method of claim 32, wherein the changes include deletion of a file.

34. The method of claim 33, wherein the changes include addition of a file.

35. A compressed common file directory for use in a mass storage system that includes a plurality of physically distinct media items, each media item being associated with a media ID and a media location identifier, said common file directory comprising:

a first data structure comprising a list of unique encoded filenames and a list of compressed media IDs, wherein each particular encoded filename comprises a filename of a particular file residing on at least one of the media items and encoded with a selected encoding scheme, and wherein each particular encoded filename is cross-referenced to a compressed media ID comprising a media ID encoded with a selected encoding scheme and associated with the particular media item containing the particular file;

a second data structure including a list of all compressed media IDs, wherein each particular compressed media ID comprises a media ID of a particular item of the plurality of media items encoded with a selected encoding scheme, and wherein each particular compressed media ID is cross-referenced to a media location identifier indicating a physical position of the particular media item within the mass storage system; and

a third data structure including a list of unencoded filenames and a list of unencoded media codes, wherein each filename is associated with a file contained on a particular item of media, and wherein each particular filename is cross-referenced to a particular media code that identifies the particular media item containing the file, wherein the third data structure is stored on at least one of the media items.

36. A file storage system, comprising:

a housings containing a plurality of physically unattached media items;

a shared storage drive selectively connectable to the media items;

a controller coupled to the storage drive;

a memory device, containing a compressed common file directory, comprising;

a first data structure comprising a list of unique encoded filenames and a list of compressed media IDs, wherein each particular encoded filename comprises a filename of a particular file residing on at least one of the media items and encoded with a selected encoding scheme, and wherein each particular encoded filename is cross-referenced to a compressed media ID comprising a media ID encoded with a selected encoding scheme and associated with the particular media item containing the particular file; and

a second data structure including a list of all compressed media IDs, wherein each particular compressed media ID comprises a media ID of a particular item of the plurality of media items encoded with a selected encoding scheme, and wherein each particular compressed media ID is cross-referenced to a media location identifier indicating a physical position of the particular media item within the housing; and

a buffer to store changes occurring to the compressed common file directory.