Optical disk storage format, method and apparatus for emulating a magnetic tape drive

Filing Information

• Patent Number: US4775969
• Application Number: US7037749
• Filing date: 04/13/1987
• Issue date: 10/04/1988
• Predicted expiration date: 05/15/2006

• U.S. Classifications: 369/53  · 369/32  ·
• International Classifications: G11B 7013 ·
• International Classifications: 36032;48;72.1;72.2 ·
• Related U.S. Application Data:
  PRIOR APPLICATION
  This is a continuation-in-part of U.S. patent application Ser. No. 863,564, filed May 15, 1986, abandoned.
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Abstract

An Optical Disk Storage system and method for the storage of magnetic tape records including an optical disk and a system for writing variable-length records to the disk with a plurality of embedded directories in close proximity to a plurality of records associated therewith. A high-level directory is constructed providing a list of addresses for the embedded directories. The embedded directories comprise a fixed maximum number of entries each indicating the length of a corresponding record. In a read operation, the high-level directory is accessed first to provide addresses for the embedded directories, with reference to positional information permanently written to the disk. Bytes of data are then counted in accordance with the stored record length information to access a record of interest. In this way, varying-length records can be efficiently stored on an optical disk divided into fixed-length data blocks.

Independent Claims | See all claims (21)

1. 1. A system for storing data from a plurality of variable-length records on an optical disk, comprising:first means for recording a plurality of variable-length data segments on said disk, each segment comprising up to a predetermined number of said records;second means for generating an embedded directory for each segment, each embedded directory comprising a number of entries, each corresponding to one of said plurality of records recorded as a segment;third means for recording on said disk said embedded directory in close physical association with the corresponding segment containing the records, andfourth means for recording a high level directory on said disk containing the physical location of each of said embedded directories.
2. 3. An optical disk for storage of information comprising a plurality of tracks, said information including:a plurality of variable-length records recorded as data segments on said disk;an embedded directory recorded on said disk in association with each of said plurality of record data segments and containing information relating to the records of the segments and in close proximity thereto, anda higher-level directory recorded at a predetermined location on said disk containing the addresses of each of the embedded directories recorded on said disk.
3. 4. A system for storing data from a plurality of variable-length records on an optical disk, comprising:first means for recording a plurality of variable-length records on said disk in segments, second means for generating an embedded directory relating to each of the recorded records of said segments and then recording each embedded directory at location on said disk which are not predetermined and which are in physical association with each segment, and memory means for storing a high-level directory at a predetermined location on said disk containing the addresses of each of said embedded directories.
4. 5. An optical disk having information stored thereon, said information including a high-level directory, a plurality of spaced apart embedded directories, and one or more data segments containing data positioned in close proximity to and in association with a corresponding one of said embedded directories, wherein the high-level directory contains address information to enable direction of a read/write head association with the disk to a particular embedded directory, and the embedded directory provides information to enable the read/write head to access variable-length data records stored in its associated data segment.
5. 6. Method of emulating a magnetic tape drive using an optical disk storage system by responding to commands from a host computer to store and reproduce data stored on such a tape, comprising the following steps, performed in a write mode:receiving data records of varying length from a host computer,writing a predetermined number of records to an optical disk without non-data separators between successive records, while counting the number of bytes written as part of each record,after said predetermined number of records have been written, writing an embedded directory to said disk in physical proximity to said predetermined number of records, said embedded directory including a byte count indicating the number of bytes of each record so recorded, andwriting a high-level directory to the disk indicating the location of each of said embedded directories on the disk.
6. 13. A method of efficiently storing data records of indeterminate length, said records organized as files comprising an indeterminate number of said records, on an optical disk storage device, said disk being organized into data storage sectors of fixed length, said disk being only accessible at the beginning of said sectors, comprising the steps of:writing a predeteremined number of said records sequentially to an optical disk for storage, while maintaining a list recording the length of each record so written;when said predetermined number of records has been written to said disk, storing said list as an embedded directory, corresponding to said records, at a location on said disk which is not predetermined, and is in close proximity to the corresponding records; andstoring the location of said embedded directory in a high-level directory at a predetermined location on said disk.
7. 18. Apparatus for storing records of varying length on an optical recording disk addressable only at predetermined positions thereon, comprising:means for writing said data records onto said disk, and for maintaining a list of their relative lengths;means for writing one or more of said lists to said disk as embedded directories, at locations determined in accordance with the lengths of the records to stored and in physical association therewith; andmeans for writing a high-level directory to said disk at a predetermined location, relating the locations of said embedded directories to said predetermined positions at which said disk is addressable.