Virtual addressing of optical storage media as magnetic tape equivalents

• US 5,455,926 A
• Filed: 06/20/1994
• Issued: 10/03/1995
• Est. Priority Date: 04/05/1988
• Status: Expired due to Fees

• Current Assignee: BankBoston, N.A (Bank of America Corp.)
• Original Assignee: Data/Ware Development Incorporated
• Inventors: Erdelsky, Philip J., Mautner, Craig D., Goodsell, Michael C., Keele, Richard V., Thompson, Sidney R., Thorpe, Tracy J.
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): Von Buhr, Maria N.
• Application Number:
  US08/265,514
• Time in Patent Office: 470 Days
• Field of Search: 364/DIG. 1, 364/DIG. 2, 395/400, 395/425, 395/500
• US Class Current: 711/4
• CPC Class Codes: G06F 11/006 Identification G06F11/2289 takes precedence
• 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: G06F 3/0664 at device level, e.g. emulation of a storage device or system
• CPC Class Codes: G11B 20/10 Digital recording or reproducing
• CPC Class Codes: G11B 20/1883 Methods for assignment of alternate areas for defective areas
• CPC Class Codes: G11B 20/1889 with discs
• CPC Class Codes: G11B 2020/10907 using pseudo-overwriting, i.e. virtually or logically overwriting data on WORM media by remapping recorded blocks to alternate areas
• CPC Class Codes: G11B 2020/1896 using skip or slip replacement to relocate data from a defective block to the next usable block, e.g. with a primary defect list [PDL]
• CPC Class Codes: G11B 2220/20 Disc-shaped record carriers
• CPC Class Codes: G11B 2220/218 Write-once discs
• CPC Class Codes: G11B 2220/2537 Optical discs

Abstract

An optical disk storage system emulates a magnetic tape subsystem by virtual addressing of data recorded on write once optical disk media having a predetermined group of available sectors for rewriting a disk ID, a predetermined plurality of bands of available sectors for rewriting a virtual tape directory to virtual tape VSNs, and, available sectors for rewriting virtual tape maps and rewriting user records, the tape maps have data portions for simulating tape marks and interblock gap and for addressing blocks of data within the virtual tapes, the virtual tape directory has pointers for pointing to tape maps, and the system rewrites the tape directory, tape maps and user records so as to function as a rewritable magnetic tape.

Claims

1. A system for recording a plurality of virtual magnetic tapes, each of which includes user records, on optical disk, said optical disk recording system comprising:

a record recording means for recording said user records of each of said plurality of virtual magnetic tapes on said optical disk, and for, at a later time, supplementally recording still further user records as represent any additions or alterations to any one or ones of the plurality of virtual magnetic tapes,

a tape map recording means for recording on said optical disk a tape map respective of each one of the plurality of virtual magnetic tapes, each tape map including pointer data pointing to a location on said optical disk of the user records of an associated one of said plurality of virtual magnetic tapes, and each tape map being recorded on the optical disk separately from an associated one of said plurality of virtual magnetic tapes, and for, at a later time, supplementally recording a new tape map or maps respective of any one or ones of said plurality of virtual magnetic tapes as are, commensurate with the ability of the recording means to record further user records, updated, and

means for recording upon the disc which individual one of possibly several historically sequential occurrences of each of the plurality of tape maps as correspond to each of the plurality of virtual magnetic tapes is newest, which newest tape maps will, in accordance with being supplementally recorded in accordance with all most recent revisions to the user records of a virtual magnetic tape, include pointer data to all most current revision user records of each virtual magnetic tape,

wherein the user records of each and any of the plurality of virtual magnetic tapes are accessed during reading by reference to the pointer data of a newest associated tape map,

wherein when a read reference proceeds through a newest tape map that is supplanting of, different than, and revised from a former tape map than such read reference is permissively to new user records that are supplanting of, and permissively different than and revised from, such User records as were accessed by the former tape map,

wherein the virtual magnetic tapes are susceptible of being any of added, deleted or altered in whole or in part by (i) the supplemental recording by the record recording means of such further added or revised user records as prove pertinent, plus (ii) the supplemental recording by the tape map recording means of a new tape map that is referenceable during reading to access said added, deleted or altered virtual magnetic tape.

2. The optical disk recording system of claim 1 further comprising;

a disk identification recording means for recording disk identification data identifying said optical disk.

3. The optical disk recording system of claim 1 further comprising:

a tape directory recording means for recording tape directory data identifying each of said plurality of virtual magnetic tapes, the tape directory including tape map pointer data pointing to a tape map respective of an associated one of the plurality of virtual magnetic tapes.

4. A system for recording on an optical disk in an optical disk drive a plurality of magnetic tapes each having user records as a corresponding plurality of virtual magnetic tapes, said optical disk recording system comprising:

a record recording means for recording said user records of each of said plurality of virtual magnetic tapes,

a tape map recording means for recording on said optical disk tape maps respective of each one of the plurality of virtual magnetic tapes, each tape map including pointer data pointing to a location on said optical disk of the user records of an associated one of said plurality of virtual magnetic tapes, and each tape map being recorded separately from an associated one of said plurality of virtual magnetic tapes, and

a tape directory recording means for recording tape directory data., the tape directory data including tape map pointer data pointing to a tape map of a respective one of the plurality of virtual magnetic tapes, and

virtual tape directory identification data recording means for recording data identifying each respective one of the plurality of virtual magnetic tapes, said virtual tape directory data being recorded separate from any of said user records.

5. The optical disk recording system of claim 4 wherein said tape directory recording means is recording a tape directory having respective tape data for each of said plurality of virtual magnetic tapes, each said respective tape data including, in addition to the pointer data pointing to a tape map of a respective one of the plurality of virtual magnetic tapes,

write protect data indicating whether the respective one of the plurality of virtual magnetic tapes is write protected,

pool type data indicating that the respective one of the plurality of virtual magnetic tapes is a one of a scratch virtual magnetic tape and a user virtual magnetic tape,

tape length data specifying the length of the respective one of the plurality of virtual magnetic tapes, and

volume serial number data for identifying the respective one of the plurality of virtual magnetic tapes.

6. The optical disk recording system of claim 4

wherein said optical disk has two sides each of which has a part of said user records, said tape maps and said tape directory, and wherein said tape directory recording means is recording tape directory data including

pointer data pointing to a respective tape map of an associated one of said plurality of virtual magnetic tapes, and

respective identification data for identifying said a respective one of said .plurality of virtual magnetic tapes.

7. The optical disk recording system of claim 4

wherein said record recording means is recording magnetic tape data including user records and tape marks separated by interblock gaps, and

wherein said tape map recording means is recording tape map data including, in addition to the pointer data pointing to a tape map of a respective one of the plurality of virtual magnetic tapes,

simulated tape mark data to indicate the presence of tape marks within a respective one of said plurality of virtual magnetic tapes,

simulated interblock gap data to indicate the presence of interblock gaps within a respective one of said plurality of virtual magnetic tapes.

8. The optical disk recording system of claim 4

wherein each of said plurality of magnetic tapes has tape marks and user records, and

wherein said tape map recording means is recording tape map data for each of said plurality of magnetic tapes having tape marks and user records, said tape map data including, in addition to the pointer data pointing to a tape map of a respective one of the plurality of virtual magnetic tapes,

type data indicating whether the pointer data is to one of said tape marks or one of said user records,

accumulated length data indicating an accumulative position within a respective one of said plurality of virtual magnetic tapes of said tape marks or said user records, and

wherein the pointer data is pointing to said user record only when said type data so indicates.

9. The optical disk recording system of claim 4

wherein said optical disk is recorded with data in sectors,

wherein each of said plurality of magnetic tapes has tape marks and user records, and

wherein said tape map recording means is recording tape map data for each of said plurality of magnetic tapes having tape marks and said user records, said tape map data including

type data serving to indicate one of said tape marks or one of said user records,

accumulated length data serving to indicate an accumulated position within a respective one of said plurality of virtual magnetic tapes of said tape marks or said user records,

wherein said pointer data serves to point to a beginning user record of all said user records of a respective one of said plurality of virtual magnetic tapes when said type data indicates one of said user records, said pointer data serving to point to one of said sectors on said optical disk in which is recorded the start of said user records of the respective one of said plurality of virtual magnetic tapes,

block length data serving to indicate the length of said user record that is pointed to by said pointer data, and

record offset data for said user record serving to indicate an offset from the beginning of said sector that is indicated by said pointer data to a location where a user record is first recorded within said sector.

10. The optical disk recording system of claim 4

wherein each of said plurality of magnetic tapes has tape marks and user records separated by interblock gaps,

wherein said tape map recording means is recording respective tape map data for each of said tape marks and said user records,

wherein said tape map data includes, in addition to the pointer data pointing to a tape map of a respective one of the plurality of virtual magnetic tapes,

type data serving to indicate one of said tape marks or one of said user records, and

accumulated length data serving to indicate an accumulative position within said virtual magnetic tape of said tape marks or said user records, said accumulated length data including the length of said user record when indicated by said type data, said accumulated length data serving to simulate said tape mark by including a predetermined tape mark length when indicated by said type data, said accumulated length data serving to simulate a respective one of said interblock gaps including a predetermined interblock gap length,

wherein said pointer data serves to point to said user record when said type data indicates one of said user records.

11. The optical disk recording system of claim 4 wherein said magnetic tape has tape marks and user records separated by interblock gaps,

wherein said tape map recording means is for recording tape map data for each of said tape marks and said user records, each of said tape map data including, in addition to the pointer data pointing to a tape map of a respective one of the plurality of virtual magnetic tapes,

type data indicating one of said tape marks or one of said user records,

accumulated length data indicating the accumulative position within said virtual magnetic tape of said tape marks or said user records, said accumulative length data including the length of said user record when indicated by said type data, said accumulative length data simulating said tape mark by including a predetermined tape mark length when indicated by said type data, said accumulative data simulating a respective one of said interblock gaps by including a predetermined interblock gap length,

wherein said pointer data point a to said user record when said type data indicates said user record, and

block length data indicating a size of said user record when said type data indicates said user record.

12. The optical disk recording system of claim 4 wherein said magnetic tape has tape marks and user records,

wherein said tape map recording means is for recording respective tape map data for each of said tape marks and said user records, each of said tape map data including, in addition to the pointer data pointing to a tape map of a respective one of the plurality of virtual magnetic tapes,

type data indicating one of said tape marks or one of said user records,

block length data indicating a size of said user record when said type data indicates said user record,

wherein the pointer data points to a sector in which the start of said user record is recorded when said type data indicates said user record, and

record offset data pointing to said user record within said sector addressed by said pointer data, said user record being recorded across sector boundaries when said size of said user record exceeds a predetermined length of said sector minus said record offset data.

13. An optical disk recording system for recording, on an optical disk where data is recorded in sectors and that is insertable in an optical disk drive, a plurality of magnetic tapes each of which has user records as a corresponding plurality of virtual magnetic tapes, said optical disk recording system comprising:

a record recording means for recording user records of said plurality of magnetic tapes as a corresponding plurality of virtual magnetic tapes,

a tape map recording means for recording a plurality of tape maps corresponding to said plurality of virtual magnetic tapes, each of said plurality of tape maps being recorded on said optical disk separate from, but pointing to, said user records of a respective one of said plurality of virtual magnetic tapes, and

a tape directory recording means for recording a plurality of tape directories each having a plurality of sectors, etch tape directory containing both an outdated tape directory and also an updated tape directory data having at least pointer data and identification data pointing to an associated one of said plurality of tape maps and identifying an associated one of said plurality of virtual magnetic tapes, said outdated tape directory data being recorded in a first sector of said tape directory so as to firstly identify an associated one of said plurality of virtual magnetic tapes, said updated tape directory data recorded in a current sector of said tape directory to currently identify an associated one of said plurality of virtual magnetic tapes.

14. The optical disk recording system of claim 13 wherein said optical disk records data in sectors, said optical disk recording system further comprising:

an identification recording means for recording upon a plurality of said sectors what comes over time to be both outdated and updated disk identification data, said disk identification data serving to identify said optical disk wherein the optical disk is re-identified by recording updated identification data, said outdated identification data being recorded in a first sector of a multi-sector tape directory to firstly identify said optical disk, said updated identification data being recorded in a current sector of said multi-sector tape directory to currently identify said optical disk, said identification data forebearing to be recorded in a last one of a predetermined number of sectors of said multi-sector tape directory until and unless a sector between said first sector and said last predetermined number of sectors proves defective.

15. The optical disk recording system of claim 13 further comprising:

an identification recording means for recording disk identification data at a first predetermined sector, said plurality of tape directories being recorded by said tape directory recording means starting at a second predetermined sector, said tape directory containing a continuation pointer serving to point to a next available sector for recording.

17. The optical disk recording system of claim 13

wherein said tape directory recording means is further for recording a plurality of directories each of which has a predetermined plurality of sectors serving to record said outdated and said updated tape directory data, a first directory of said plurality of directories being recorded at a predetermined location, said first directory having a last sector serving to record pointer data pointing to a next directory and also having a last sector serving to record pointer data pointing to a successive next directory of said plurality of directories, said plurality of directories also including a current directory having a current sector serving to record said updated tape directory data,

wherein re-recording of said tape directory in a predetermined number of last sectors of each of said directories is foregone until and unless a sector between said first sector and said last predetermined number of sectors is defective,

wherein said outdated tape directory data and said updated tape directory each contain a continuation pointer serving to point to a next available sector for separately recording said user records, said tape maps and said next directory, and also

wherein the identification recording means serves to record disk identification data at a first predetermined location recorded separately from said first directory.

16. The optical disk recording system of claim

wherein said tape directory recording means is recording a plurality of directories of which directories has a predetermined plurality of sectors for recording said outdated and updated tape directory data, a first directory of said plurality of directories being recorded at a predetermined location, said first directory having a last sector serving to record pointer data pointing to a next directory, and also having a last sector serving to record pointer data pointing to a successive next directory, a of said plurality of directories, and a current directory of said plurality of directories having a current sector serving to record said updated tape directory data, said updated tape directory data forebearing to be recorded in a last predetermined number of sectors of each of said plurality of directories until and unless a sector between said first sector and said last one of a predetermined number of sectors is defective.

18. A method for identifying a selected one of a plurality of virtual magnetic tapes recorded on an optical disk that is recording data in sectors and that is insertable in an optical disk drive in a system that includes at least a computer with a memory, said optical disk having directories of virtual magnetic tapes recorded in one or more sectors of a plurality of directories each of which directories spans a plurality sectors, said directories of virtual magnetic tapes identifying all said plurality of virtual magnetic tapes, said method comprising the steps of

first searching the optical disk by reading in sequence said directories and then the sectors of each successive directory until a lowest unrecorded sector in a lowest directory is detected, then

causing said reading to back up one sector from the lowest detected unrecorded sector, then

reading the directory of virtual magnetic tapes recorded in this next-to-lowest sector into said memory, and then

second searching the directory of virtual magnetic tapes in said memory to currently identify a selected one virtual magnetic tape.

19. The method of claim 18 wherein said method further comprises after the reading the steps of

updating said directory of virtual magnetic tapes in said memory by deleting data of a one of said one or ones of said plurality of virtual magnetic tapes, or by adding data of another one or ones of said plurality of virtual magnetic tapes, or by both adding and deleting data, and

writing said updated tape directory in said lowest unrecorded sector of said lowest directory.

20. The method of claim 18 wherein said tape directory data further includes pointer data pointing to a next directory, said method further comprising, after the reading, the steps of

recording pointer data in a last sector of said lowest directory, said pointer data pointing to a next, next-to-lowest, directory, and wherein said reading further comprises

determining if said next-to-lowest sector stores pointer data, and

IF said next-to-lowest sector stores pointer data THEN searching in sequence said next directory for a first unrecorded sector therein ELSE IF said next-to-lowest sector does not store pointer data THEN reading tape directory data into memory.

21. The method of claim 18 wherein said optical disk has an identification band having a plurality of sectors, the identification band serving to record disk identification data, said optical disk being re-identified by recording updated identification data in successive ones of the sectors of said identification band, said method further comprising the step of

searching by reading in sequence the plurality of sectors of said identification band until a first unrecorded sector is detected, then

causing said reading to back up one sector so as to read identification data recorded in that sector into said memory, then

updating said identification data in said memory with updated identification data, and then

recording said updated identification data in said first unrecorded sector.

22. A method of writing a plurality of virtual magnetic tapes on an optical disk in an optical disk drive in and by a system that receives magnetic tape data including user records, said system having at least a computer and memory for writing the plurality of virtual magnetic tapes, said method comprising the steps of

organizing said user records of said magnetic tape data into a plurality of virtual magnetic tape user records,

writing said plurality of virtual magnetic tape user records on said optical disk,

generating a corresponding plurality of tape maps for said plurality of virtual magnetic tapes, said plurality of tape maps having pointers respectively pointing to each said plurality of virtual magnetic tape user records, and

writing said plurality of tape maps on said optical disk separate from and after, the writing of said plurality of virtual magnetic tape user records.

23. The method of claim 22 wherein said step of generating said plurality of tape maps comprises the sub-steps of

generating block type indicators for indicating respective tape marks or respective ones of said plurality of virtual magnetic tape user records,

generating said respective record pointers pointing to respective ones of said plurality of virtual magnetic tape user records, and

generating block length indicators indicating the length of respective ones of said plurality of virtual magnetic tape user records.

24. The method of claim 22 wherein said method further comprises the steps of

generating a plurality of tape map pointers respectively pointing to respective ones of said plurality of tape maps, and

writing said plurality of tape map pointers on said optical disk separate from, and after, writing said at plurality of tape maps.

25. The method of claim 22 wherein said method further comprises the steps of,

generating a plurality of tape map pointers respectively pointing to said plurality of tape maps corresponding to said plurality of virtual magnetic tapes,

generating a continuation pointer serving to point to an available address space on said optical disk,

writing said tape map pointers on said optical disk separate from, and after, writing said plurality of tape maps, and

writing said continuation pointer on said optical disk separate from and after, writing said plurality of tape maps, said written continuation pointer serving to point to an available address space on said optical disk.

26. The method of claim 22 wherein said optical disk records data in sectors and wherein said step of generating a plurality of tape maps comprises the substeps of

generating block type indicators indicating respective tape marks or respective ones of said virtual magnetic tape user records,

generating said record pointers having at least respective sector addresses and respective sector offsets pointing to said respective virtual magnetic tape user records when said block type indicators indicate said respective virtual magnetic tape user records, and

generating block length indicators indicating the length of said respective virtual magnetic tape user records, said block length indicators, said sector addresses and said sector offsets for writing said respective virtual magnetic user records across one or more sector boundaries.

27. A method for reading a plurality of magnetic tapes recorded on a single optical disk in an optical disk drive by, and by use of, a pre-existing computer system for reading magnetic tape data from magnetic tapes having user records, the user records that are read from the optical disk being recorded on said optical disk as a plurality of virtual magnetic tapes each of which has virtual magnetic tape user records, said optical disk recording tape map data for said plurality of virtual magnetic tapes, said tape map data including pointers respectively pointing to said virtual magnetic tape user records of said plurality of virtual magnetic tapes, said tape map data being recorded on said optical disk separate from said virtual magnetic tape user records, said method comprising the steps of

reading into said memory said tape map data,

selecting from tape map data at least one of said record pointers serving to point to at least one of said virtual magnetic tape user records, and

reading into said memory said at least one virtual magnetic tape user record.

28. The method of claim 27 wherein said tape map data includes a tape map for each of said plurality of virtual magnetic tapes, each of said tape maps as are associated with each of said plurality of virtual magnetic tapes including a plurality of record pointers respectively pointing to said virtual magnetic tape user records f an associated one of said plurality of virtual magnetic tapes, and wherein said step for generating optical disk drive commands to read into said memory said tape map data further comprises the sub-step of

reading into said memory at least one tape map for accessing said user records of a respective one of said plurality of virtual magnetic tapes.

29. The method of claim 27 wherein said tape map data includes at least one tape map for each of said plurality of virtual magnetic tapes, each of said at least one tape map including a plurality of record pointers respectively pointing to said virtual magnetic tape user records, wherein said optical disk records a tape directory pointing to said at least one tape map, and wherein said method further comprises the steps of

reading into said memory said tape directory, and

selecting from said tape directory said at least one tape map as corresponds to at least one of said plurality of virtual magnetic tapes.

30. A method of maintaining a plurality of virtual magnetic tapes on a plurality of optical disks recorded in optical disk drives in a system that serves to emulate a magnetic tape subsystem that controls magnetic tape drives to read or writing magnetic tape user records and that is connected through a channel to a host computer transmitting channel commands within channel data formats, said system including a computer with memory for communicating through said channel commands within channel data formats, said magnetic tape user records being recorded on optical disks as the plurality of virtual magnetic tapes, each of said optical disks recording a plurality of tape maps each respectively for a corresponding one virtual magnetic tape, each tape map serving to point to respective virtual magnetic tape user records that are recorded separate from the tape map, said method comprising the steps of

receiving one or more channel commands through said channel directing the accessing of magnetic tape user records on a one of the plurality of magnetic tapes, and

reading said plurality of tape maps in order so as to determine a respective one of said plurality of virtual magnetic tapes in which is recorded said magnetic tape user records.

31. A method of claim 30 wherein each optical disk of said plurality of optical disks further records a plurality of tape directories one of which directories is a current directory that is a last recorded one of said tape directories, each of said plurality of tape directories having tape map pointers serving to point to a tape map and a continuation pointer serving to point to an available address on said optical disk, said method further comprising the steps of

reading a current directory into said memory,

determining from said current directory an address on said optical disk which address is a location of one tape map of said plurality of tape maps,

determining from said current directory an available address,

receiving a write command through said channel requesting the writing of at least one user record within said magnetic tape,

receiving said at least one user record through said channel,

storing said at least one user record in said memory,

writing said at least one user record on said optical disk at said available address,

updating said one tape map in said memory updated to point to the location of said at least one user record written on said optical disk,

writing said updated tape map on said optical disk,

updating said current tape directory in said memory with another one of said tape map pointers to point to the location of said updated tape map written on said optical disk,

updating said updated tape directory with another available address, and

writing said updated tape directory as said current tape directory.

32. The method of claim 31 wherein each optical disk of said plurality of optical disks records on each side a tape directory having tape map pointers pointing to said at least one tape map recorded on a respective optical disk side each recording at least one of said plurality of virtual magnetic tapes, said tape directory listing said respectively recorded virtual magnetic tapes, wherein each optical disk side of said optical disk has a disk identification identifying said optical disk and said optical disk side, said system storing cross reference data cross referencing optical disk sides to virtual magnetic tapes, said method further comprising the steps of

reading said disk identification, and

updating said cross reference in said memory to cross reference said optical disk side and said respective at least one virtual magnetic tape.

33. The method of claim 30, wherein said method further comprises the steps of

receiving a write command through said channel requesting the writing of at least one user record within said magnetic tape,

receiving said at least one user record through said channel,

storing at least one user record in said memory,

generating optical disk drive commands to write said at least one user record on said optical disk,

updating in said memory said one tape map to point to the location of said at least one user record written on said optical disk, and

writing said one tape map on said optical disk.

34. The method of claim 30 wherein said at least one tape map comprises map data having at least respective record pointers, record lengths and record offsets for said virtual magnetic tape user records recorded across sector boundaries on said optical disk, wherein said optical disks each further record a tape directory having at least tape map pointers pointing to respective said at least one tape map, said method further comprising the steps of

reading said tape directory on said optical disk into said memory,

receiving a read command through said channel requesting the reading of said a one of said plurality of magnetic tape user records within said magnetic tape,

determining an address from said tape map data on said optical disk of a location of a one of said virtual magnetic tape user records as is requested by said read command,

reading said the one of said plurality of virtual magnetic tape user records recorded on said optical disk that was requested by said read command,

storing said read one virtual magnetic tape user record that was read from said optical disk drive into said memory, and

transmitting through said channel said read virtual magnetic tape user record from said memory, said at read virtual magnetic tape user record being formatted during transmission as a magnetic tape user record.

35. The method of claim 30 wherein said optical disks each further record at least one tape directory one of which is a current directory being the last recorded one of said plurality of tape directories, said plurality of directories being recorded in a predetermined band of sectors, each said plurality of tape directories containing tape map pointers serving to point to a respective one of the plurality of tape maps and a continuation pointer serving to point to an available address on said optical disk, said method further comprising the steps of

reading into said memory sequential sectors of said predetermined band of sectors,

determining a last recorded sector in said predetermined bands of sectors,

reading into said memory said last recorded sector containing said current directory, and

determining from said current directory an address on said optical disk of the location of a one of said plurality of tape maps.

36. The method of claim 30 wherein said system stores a cross reference between sides of said optical disks and said at least one virtual magnetic tape, wherein said optical disk sides record a tape directory identifying said at least one virtual magnetic tape recorded on said respective optical disk side, and wherein each of said optical disk sides has a disk identification, said disk identification being recorded in a sector before a first available sector in a predetermined band of sectors on said optical disk side, said method further comprising the steps of

reading said disk identification into said memory by searching said predetermined band of sectors for a last recorded sector on one of said optical disk sides,

determining from said disk identification and from said cross reference that said optical disk side is referenced to one of said plurality of virtual magnetic tape,

reading said tape directory into said memory, and

determining that said tape directory identifies a one of said plurality of virtual magnetic tapes.

37. A method, performed on an optical disc that may be written but once in each area thereof,

of recording a plurality of virtual magnetic tapes each of which virtual magnetic tapes includes user records, and

of re-recording revised ones of the virtual magnetic tapes particularly as are so revised by incorporation of new and updated user records,

so that each of the user records of each of the virtual magnetic tapes may be addressably accessed in its most currently revised form as if it were a record upon a magnetic tape, the method of recording and re-recording virtual magnetic tapes on an optical disc comprising:

first recording on the optical disc, all in a first area and each at an addressable location,

the user records of each of the virtual magnetic tapes, and, at later times,

still further user records as represent any additions or alterations to any one or ones of the virtual magnetic tapes; and

, at the conclusion of each recording of the user records of one or more virtual magnetic tapes,

second recording on the optical disc, at an addressable location of a second area thereof that is separate from the first area, tape maps, each of which tape maps is individually uniquely associated with a corresponding one of the virtual magnetic tapes, each of which tape maps includes pointer data pointing to the addressable locations on said optical disc of all the most current user records of an associated one of the virtual magnetic tapes; and

also at the conclusion of each recording of the user records,

third recording upon the disc, at a dedicated area thereof that is separate from the first area, a tape directory, which tape directory contains pointers to the addresses of the newest and most current tape map for each and every virtual magnetic tape, which newest tape map for each and any particular virtual magnetic tape will contain pointer data pointing to the addressable locations on the optical disc of all the most current revisions of all the user records of that particular virtual magnetic tape;

wherein each and any particular sought-after one of the user records on each and any particular sought-after one of the virtual magnetic tapes may be addressably accessed in its most currently revised form just as if it were a record upon a magnetic tape by reading tape directories to find a most current one such tape directory, and then, by reading a pointer for to the tape map of a particular sought-after virtual magnetic tape that is contained in this newest tape directory, reading the most current tape map for this particular sought-after virtual magnetic tape, and then, by reference to the pointers to the newest user records that are contained in this newest tape map, reading the particular sought-after one of the user records.

38. A method of addressably recording and re-recording on an optical disc a multiplicity of user records that are contained in plurality of virtual magnetic tapes, the optical disc recording and re-recording method comprising:

recording and re-recording at first times any of the user records, and any selectively updated ones of the user records, of each of the plurality of virtual magnetic tapes, this recording and re-recording serving to record all the user records and all the selectively updated user records each in its own particular addressable location in a first area on the optical disc; and

then, at a time subsequent to the each of recording or re-recording of the records at the first times,

recording and re-recording at second times after the first times, tape maps, and successor tape maps, each in a second area, separate from the first area, on the optical disk, each tape map being associated with a corresponding one virtual magnetic tape, each tape map including pointer data pointing to addresses on the optical disc of each most-recently recorded one of all the user records of the associated one virtual magnetic tapes;

wherein each successor, newer, tape map as is associated with a one virtual magnetic tape supersedes and renders obsolete when written the immediately earlier and older tape map as was previously associated with the same one virtual magnetic tape;

wherein each successor, newer, tape map, includes, by virtue of being generated at a second time subsequent to the occasion of a previous recording or re-recording of user records at a first time, pointer data pointing to at least one most newly recorded user record of a virtual magnetic tape, but may also contain pointer data pointing to user records of the same virtual magnetic tape that were not immediately just recorded or rerecorded in the immediately preceding first time;

wherein a recording surface of the disc is conserved because, although only changed and selectively updated user records are rewritten, all the most current user records of any particular one virtual magnetic tape may be addressably accessed through a single newest tape map associated with that particular one virtual magnetic tape.

39. A method of recording on an optical disc a plurality of magnetic tapes each having user records, the optical disc recording method comprising:

first recording in a first area of the optical disc the user records of each of the plurality of virtual magnetic tapes;

then

second recording in a second area, separate from he first area, of the optical disc tape maps respective of each one of the plurality of virtual magnetic tapes, each tape map including pointer data serving to point to a location on said optical disc of the user records of an associated one of said plurality of virtual magnetic tapes; and

then

third recording, in an area of the optical disc separate from the first area, tape directory data, the tape directory data including tape map pointer data serving to point to a tape map of a respective one of the plurality of virtual magnetic tapes.

40. The optical disc recording method according to claim 39 that, after the third recording, further comprises:

fourth recording, in an area of the optical disc separate from the first area, virtual tape directory identification data, the virtual tape identification data serving to identify each respective one of the plurality of virtual magnetic tapes.

41. A method of recording on an optical disc a plurality of magnetic tapes, each of which magnetic tapes includes user records, as a plurality of virtual magnetic tapes, said method of recording the user records of magnetic tapes as virtual magnetic tapes on optical disc comprising:

first recording user records of a plurality of magnetic tapes on the optical disc at a first area thereof as addressable records corresponding to a plurality of virtual magnetic tapes;

second recording, in a second area of the optical disc separate from the first area, a plurality of tape maps corresponding to the plurality of virtual magnetic tapes, each of which plurality of tape maps points to all the user records of a respective one of the plurality of virtual magnetic tapes;

repeating the first recording and the second recording as is required to do any of add, change and delete user records, and add, change or delete virtual magnetic tapes;

while after each iteration of the first and the second recording

third recording in a dedicated area of the optical disc a tape directory having at least pointer data pointing to the most recent one of each of the plurality of tape maps as is associated with each of the plurality of virtual magnetic tapes, the dedicated area of the optical disc ultimately coming to containing outdated tape directories and also a most currently updated tape directory, said outdated tape directories being identifiable from the most currently updated one tape directory because all tape directories are recorded seriatim in the dedicated area, and a last one such recorded, which is necessarily presently last in the dedicated area, is the most currently updated one tape directory;

wherein the most currently updated one tape directory contains pointers to the most current tape map as is associated with each of the plurality of virtual magnetic tapes, and each most current tape map, in turn, contains pointers to all the most current ones of all the user records that are upon the associated virtual magnetic tape.