WO1984004990A1

WO1984004990A1 - A system and method for organizing and managing data stored on an informational disk

Info

Publication number: WO1984004990A1
Application number: PCT/US1984/000817
Authority: WO
Inventors: Juan A Rodriguez; A Kenneth Johnson; John W Mcintosh; James Kent Harness; Hadley Stacey; John Rundell; Frederick Ii Parham
Original assignee: Storage Technology Partners
Priority date: 1983-06-07
Filing date: 1984-05-25
Publication date: 1984-12-20
Also published as: EP0145751A1

Abstract

A system and method for organizing data on a removable optical disk. The surface area of the disk is divided into concentric data bands (12, 13, 14), each comprising sufficient disk surface area upon which a large number of concentric data tracks may be written. Concentric servo tracks (16, 17, 18), wider than the data tracks, are used to separate adjacent data bands. Each data band utilizes one data track (62) as an address track upon which data identifying the particular data band is pre-written. One data band (60) is set aside as an index band into which indexing information, identifying what data is written in each band, may be written. A desired data record or file can be quickly accessed by first using the index band to identify the address of the band where the desired data is located, and then by directly and rapidly accessing the identified band.

Description

A SYSTEM AND METHOD FOR ORGANIZING AND MANAGING DATA STORED ON AN INFORMATIONAL DISK

BACKGROUND OF THE INVENTION

This invention relates to data storage systems wherein information is stored on a rotating disk, and more particularly to a system and method for organizing and managing the data stored on an informational disk.

Heretofore data storage systems have principally been one of two types: (1) direct access storage systems wherein desired data records are stored on one of several tracks of a rotating disk or platter; and (2) sequential storage systems wherein desired data records are stored on one or more data tracks of a moving tape. In order to provide direct access capabilities, a direct access storage system selectively positions a read/write head along a radial axis of a rotating disk. As the disk rotates, the read/write head may thereby directly access any segment of a given data track on the disk by merely waiting until the desired segment of the track rotates under the head. In contrast, sequential storage systems typically use a long tape, usually wound on reels or spools, that is driven past a stationary read/write head at a desired speed. Information stored at one end of the tape can only be accessed by sequentially moving the entire tape past the read/write head until the desired portion of the tape is next to the head.

Both types of data storage systems--direct access and sequential--are useful for certain applications. For example, if the amount of data to be stored is relatively small, but must be accessed quite frequently, then a direct access storage system, such as a magnetic disk system, has heretofore been the preferred storage approach. Data records relating to inventory, accounts, and the like are the type of data for which a direct access storage system is best suited. If, on the other hand, the amount of data being stored is relatively large, or need not be accessed v ery often, then a sequential access storage system, such as is realizable with a magnetic tape system, has been the preferred storage approach. Historical or encyclopedia-type information, that may only need to be occassionally accessed, is the type of data for which a sequential access storage system may be most effective.

With the development of optical disk storage systems, wherein massive amounts of data may be stored on a single disk, numerous questions have arisen as to how best to utilize the available disk storage capacity. (A single optical disk, for example, may be able to store up to 4-6 gigabytes of datal) On the one hand, an optical disk storage system has the inherent direct access characteristics of a magnetic disk system in that any given track can, at least in theory, be accessed by merely radially moving the read/write head until the desired track is located. Unfortunately, because of the large number of tracks on an optical disk, the actual time required to locate and access a given track could, if conventional accessing and formatting techniques are used, take longer than the access time that has heretofore been achievable with magnetic disk systems. On the other hand, the large storage capacity of optical disk systems lends itself nicely to a sequential access storage system wherein extremely long sequential files can be stored. Thus, how an optical disk storage system can best be utilized poses an interesting challenge to an architect of an optical disk storage system.

An attendant problem associated with the large amounts of data stored on an optical disk is indexing, that is, keeping track of where identified information is stored on the disk. If traditional indexing methods are used -- wherein one index entry is made for every 4-6 Kbytes of data -- the size of the index itself may become extremely large, especially for the large data files or records that could be stored on an optical disk.

Accordingly, there is a need in the optical disk art, and other informational disk art wherein large amounts of data are stored on a single disk, for a disk storage system that efficiently and flexibly utilizes the large storage capacity of such systems, whether through direct, access, sequential access, or other techniques; and wherein the indexing task associated with storing such large amounts of data does not become unmanageably large.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a disk format for use with an informational disk of a disk storage system that lends itself to excellent direct access performance.

It is a further object of the present invention to provide such an informational disk format that also lends itself to excellent sequential access performance.

Still another object of the invention is to provide such informational disk format that may be easily used with both small and very large data records.

A further object of the invention is to provide an informational disk for use on a disk storage system wherein indexing information is easily stored on the disk without requiring a large amount of disk storage space.

Still a further object of the invention is to provide a method for managing the information stored on an informational disk that is flexible and adaptable for use with a wide variety of storage applications.

The above and other objects of the invention are realized by dividing the informational disk into subdivisions or bands of data. In the preferred embodiment, wherein an optical disk is disclosed, there may be over 700 such data bands on a given disk. A band of data advantageously represents the unit that can be physically addressed and accessed by the radial arm upon which is found the read/write head. Moreover, a data band represents the unit that can be logically addressed to access a given file or record. Further, the optical disk drive hardware is able to selectively search for a given data band at very high speeds.. Advantageously, the data band is also the element that can be indexed.

One data band on each disk is maintained as an index band. As the removable informational disk is inserted into a disk drive, the contents of the index band may be loaded into a memory device, such as a random access memory (RAM). When a desired data file or record is to be accessed, the drive determines the data band where the desired file is located by looking in the RAM, and. then initiates a high speed search to the identified band.

Each data band comprises a large number of data tracks. One data track in each band is pre-written on the disk as an address track that is used to uniquely identify the data band. The other data tracks may be written with variable length data files. Thus, a lengthy data file (normally accessed sequentially) may be written in a given data band, or smaller data files (normally accessed directly) may also be written in a desired band. Advantageously, whether accessed sequentially or directly, the data in a given data band may be accessed with almost equal speed. In the preferred embodiment, adjacent data bands on the disk are separated by coarse servo tracks, which servo tracks are typically 3-5 times the width of the data tracks. These coarse servo tracks are used by a coarse servo system of the disk drive to position and maintain the read/write head of the disk drive over a desired band. Access to a desired track within a selected band is achieved by a fine servo system.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the present invention will be more apparent from the following more particular description, presented in connection with the accompanying drawings wherein:

FIG. 1 is a block diagram of a coarse/fine servo system used in an optical disk data storage system, and illustrates the preferred environment in which the invention could be used;

FIG. 2 schematically shows the principle elements of FIG. 1;

FIG. 3 is a side view of an optical disk drive and schematically shows the relationship between the optical disk, fixed and moving optics packages, and a linear actuator for controllably positioning the read/write head;

FIG. 4 is an expanded view of a segment of the optical disk surface and further illustrates the data bands separated by coarse servo tracks; and

FIG. 5 is an expanded view of a portion of a data band, and illustrates a representative organization thereof. DETAILED DESCRIPTION OF THE INVENTION

The present invention is best understood by reference to the accompanying drawings wherein like numerals will be used to describe like elements or parts throughout. It is to be emphasized, that while a preferred embodiment of an optical disk drive is disclosed below, which embodiment presents the best mode contemplated for carrying out the invention, the present invention could be used with almost any disk or disk drive configuration, now existing or yet to be conceived.

FIG. 1 shows a block diagram of a coarse/fine servo system of a type with which the present invention could be used. The various optical paths associated with the system shown in FIG. 1 are illustrated as bold lines, whereas electrical paths are indicated by fine lines. Mechanical coupling, as occurs between a carriage actuator 24 and the carriage optics 23, is indicated by a dashed line.

Referring next to both FIG. 1 and FIG. 2, the optical drive of a preferred system can be explained. The optical drive system of the preferred embodiment allows reading and writing from and to the surface of a disk 11 having a rotational axis 10 and a plurality of concentric data bands 12-14 (shown in FIG. 2). Each of the data bands includes space on the surface of the disk where a plurality of data tracks could be concentrically written about the rotational axis. The surface of the disk 11 has pre-recorded thereon, during manufacture, a plurality of optically readable servo tracks 16-19, concentrically and uniformly spaced about the rotational axis of the disk and positioned between the data bands. One data track, preferably adjacent to a servo track, is pre-written during manufacture with an address that uniquely identifies the data band where the address track is located.

The disk 11 is rotated about its axis 10 by conventional means. An optical read/write head, depicted by the carriage optics block 23, is positioned adjacent to the surface of the disk 11. Carriage actuator 24 selectively moves the read/write head along a radial axis 20 (FIG. 2), thereby moving the carriage optics 23 in a radial direction with respect to the disk 11 in order to access the data bands thereon. Mechanical motion of the carriage optics 23 is depicted in FIG. 2 as a dotted line 45, with motion being possible in both directions as indicated by the double headed arrow 45'.

A fine read/write servo illuminator and detector 25 (FIG. 2) projects read or write light beam(s) 52' to the surface of the disk 11 so as to access data tracks thereon. In order to access the disk surface, this beam 52' is reflected by a fine tracking mirror 26, passes through a beam combiner and separator 27, as well as through the carriage optics 23. Included within the illuminator and detector 25 is a read detector 25b (FIG. 1) that reads light which has been reflected from the accessed recorded data track. This reflected light passes through the carriage optics 23 and beam combiner and separator 27 before reaching the read detector 25b. The read detector converts this light to an equivalent electrical signal(s). This read electrical signal is, in turn, supplied to a data read system 25c, and to a fine access/tracking servo system 25d.

The servo system for access to and tracking of the coarse servo tracks includes a coarse illuminator 30 which projects light, represented as dashed double-dot lines in FIG. 2, through a coarse servo beam separator 36, a beam combiner and separator 27, and the carriage optics 23 onto a relatively broad portion 11a of the disk surface (FIG. 2). An optical detector 31 detects reflected light, represented as dashed single-dot lines in FIG. 2, from the portion 11a of the disk surface. It is noted that the illuminated portion 11a of the disk surface spans at least the distance between two coarse servo tracks, and thereby always illuminates at least one coarse servo track. As shown in FIG. 2, light is reflected from the portion 11a of the disk 11 between servo tracks 16 and 18 with the servo track 17 being projected onto a coarse detector 31.

The output of the coarse detector circuitry 31 is a coarse track position error signal (PES), which signal has an amplitude proportional to the location at which the reflected radiation from the illuminated coarse servo track falls on the face of the detector 31. This error signal from the detector 31 is applied to a coarse access/tracking system 34. This system is connected in a servo loop with the actuator 24, which actuator moves the read/write head (represented schematically by the carriage optics 23) into radial proximity of a selected servo track so that the fine access and tracking system 25d can accurately position read or write beams on a selected data track.

As indicated previously, light reflected from a single data track on the disk is passed by means of the carriage optics 23, beam separator 27, and tracking mirror 26, and is detected by read detector 25b, the output of which is applied to the fine access/tracking servo system 25d. The read or write beams 52' from the illuminator 25a are moved radially with respect to the optical disk 11 by means of the tracking mirror 26, thereby providing for fine selective control of the beam's radial position. The tracking mirror 26, which may be a conventional galvanometer controlled mirror(s), is controlled by the fine access/tracking servo system 25d.

In order to discriminate radiation reflected from servo tracks from that reflected from data tracks or other areas of the disk surface, the servo tracks preferably have an on/off (reflectivity-high/reflectivity-low) pattern placed therein that may be conceptually thought of as a dashed line, as shown best in FIG. 4. Further, the servo tracks are preferably three- to five times the width of the data tracks. The servo tracks provide improved data track following capability by providing coarse tracking control of the read/write head. The coarse tracks are also used to permit rapid random access to a desired data band, regardless of whether any data has been recorded in the fine track area. This provides the ability to skip to randomly selected data bands for reading or writing. Seeking to a selected band may be accomplished by counting coarse tracks, or by any other suitable track seeking technique commonly used in magnetic disk drives.

FIG. 3 is a side view that schematically shows the relationship between the optical disk 11 and a moving optics package 40 that is driven by the carriage actuator 24 into a read/write relationship with any of the tracks on the disk 11. .The carriage actuator 24 may be realized with a linear motor, such as a voice coil motor, that includes a stationary magnet 41 and a moveable coil 49. The optical path for either the read or write light beam(s) to the surface of the disk 11 includes an objective lens 50, mirror 42, telescope lens 43, and mirror 44. Light is transmitted to and from the moving optics package 40 through a suitable optics package 47 mounted to a fixed optic plate 48 on which the remainder of the optics are mounted. The details associated with this optics package are not pertinent to the present invention. Any suitable technique could be used within the optics package to achieve the desired reading and writing capabilities.

FIG. 4 further details the concept of a data band that is used in formatting an optical disk in accordance with the present invention. Data bands are placed concentrically about the center of the disk and are separated by coarse servo tracks 16-18. There may be over 700 data bands on a single optical disk, and each data band may have approximately 50-60 data tracks associated therewith. Each data track may, in turn, have a storage capacity of around 118 Kbytes. One data band per disk is set aside as an index band 60. Indexing information is written into this band to identify the types of files or records, and/or the contents thereof that are written in the other optical data bands on that same disk. (For purposes of this application, the terms "data file" and "data record" are used synonymously to indicate a collection of data bytes that is stored as a group.)

FIG. 5 is a representative expanded view of how a given data band could be organized. The organization of FIG. 5 is given by way of example only, and is given to illustrate the flexibility that exists through use of the data band concept. The servo track 17 separates the data band 13 from an adjacent data band 12. A first data track within the data band 13 is an address track 62. This address track has information written thereon, during manufacture of the disk, that uniquely identifies the data band 13. During a rapid seek operation to a desired band, the rapid seek servo would typically count servo tracks to get to what the servo believes is the desired band. However, once there, the address track would be

read in order to confirm that the desired band has indeed been accessed.

A first data file or record 64 within the data band 13 of FIG. 5 may comprise 4 data tracks. A second data file 66 may comprise only a portion of another data track; while a third data file 68 may comprise another portion of this same data track 72. A fourth data file 70 may comprise two data tracks. A fifth data file 72 may comprise a large number of data tracks, e.g., the balance of the data tracks remaining in the band. As emphasized in FIG. 5, an important feature of the present invention is allowing data files or data records to be variable in length. Thus, large data records, such as are common in sequential access storage applications, may be stored on the disk; as may smaller data files or records, as are common in direct access storage applications.

As mentioned previously, the indexing function of the present invention has been moved to the optical drive. That is, an indexing band 60 (FIG. 4) is placed on the disk itself. During processing of an optical disk, e.g., during the initialization routine, the contents of the indexing band may be advantageously loaded into a RAM, or other suitable memory element. Locating a band wherein a desired data record is stored can then be quickly done at electronic signal processing speeds by electronically scanning the contents of the memory device. The identified band can then be rapidly accessed through a high speed search (seek) operation of the coarse servo system. Response times using such an approach, measured from the time the request is made until the desired data is retrieved, are very competitive with comparable data retrieval operations performed by magnetic disk drives. Advantageously, the present invention is not limited to a particular type of optical disk media, or coding scheme used to record the data on the media. Moreover, any type of marking mechanism could be used to mark the data on the media; and it matters little whether the media exhibits high or low reflectivity at a desired mark, so long as sufficient contrast exists between marks and non-marks so that data can be properly distinguished and read by whatever optical read mechanism and/or encoding scheme is employed. Further, any type of disk or disk data storage system could employ the present invention; although, as a practical matter, the invention is best suited for use with storage media having very large storage capacities, such as are achieved with optical disk media used with optical storage devices.

It is also to be noted that the disk formatting and management scheme of the present invention is not limited to removable media. However, again as a practical matter, it is disk storage systems employing removable media having large storage capacities for which the invention is best suited.

The concept of data bands, including a data band that functions as an index band, and means for uniquely identifying each data band, allows great flexibility in configuring different systems for different applications. That is, the present invention could be easily used with storage systems coupled to a single central processing unit (CPU), or to multiple CPU's. Further, the invention is especially versatile for use in a system wherein removable media can be automatically and selectively retrieved by the drive mechanism, such as in a juke-box type system.

While a particular embodiment of the invention has been shown and described -- namely an optical disk drive application -- various modifications could be made thereto that are within the true spirit and scope of the invention. The intended claims are, therefore, intended to cover all such modifications.

Claims

CLAIMS What is claimed is:

1. A system for organizing data stored on a disk that is mounted in a disk storage system, said disk storage system being adapted to store and access data records, written on said disk, said system comprising: a plurality of data bands concentrically positioned on said disk; identifying means for uniquely identifying each of said data bands; and indexing means for storing on said disk indexing information relating to the data stored in each of said data bands.

2. The system of Claim 1 wherein each of said data bands comprises a plurality of concentric data tracks positioned adjacent to each other on said disk.

3. The system of Claim 2 wherein adjacent data bands are separated by a servo track, said servo track having characteristics that distinguish it from one of said data tracks.

4. The system of Claim 3 wherein the distinguishing characteristic of said servo track is that it is at least twice as wide as one of said data tracks.

5. The system of Claim 3 wherein the distinguishing characteristic of said servo track is that it is three to five times as wide as one of said data tracks.

6. The system of Claim 3 wherein said identifying means for uniquely identifying each of said data bands comprises an address track within said data band, said address track having a unique address written therein.

7. The system of claim 6 wherein said address track comprises one of said data tracks adjacent to said servo track.

8. The system of Claim 3 wherein said indexing means comprises a selected one of said data bands wherein indexing information may be written.

9. The system of Claim 8 wherein each of said data bands comprises at least 50 data tracks.

10. The system of Claim 9 wherein said disk has at least 700 of said data bands thereon.

11. A system for storing and accessing data on an optical disk, said disk being configured for detachable mounting in an optical disk drive storage unit, said disk drive storage unit having means for rotating said disk; means for controllably writing data on said disk at desired radial positions thereof, whereby concentric data tracks are created as said writing occurs and said disk rotates; and means for selectively reading the data contained in a specified segment of a desired data track or tracks; said system comprising: means located on said disk for grouping data tracks into a plurality of data bands; identifying means located on said disk for uniquely identifying each of said data bands, said reading means of said optical disk drive storage unit being able to read said identifying means in order to identify a desired data band; and means located on said disk for indexing the data stored in each of said data bands.

12. The system of Claim 11 wherein said grouping means comprises a plurality of spaced-apart servo tracks placed on said disk, the data tracks lying between adjacent servo tracks comprising one of said data bands.

13. The system of Claim 12 wherein said identifying means comprises a data track within said data band into which a unique address is written.

14. The system of Claim 13 wherein each of said data bands comprises at least 50 data tracks, and wherein there are at least 700 of said data bands on each optical disk.

15. The system of Claim 13 wherein said indexing means comprises one of said data bands dedicated to storing indexing information.

16. A method for storing and accessing data on a removable optical disk adapted for use in an optical disk storage system, said method comprising the steps of:

(a) formatting said disk so as to divide it into a plurality of data bands, each of said data bands having a sufficient storage capacity to store at least one relatively large data file or a plurality of relatively smaller data files;

(b) uniquely identifying each of said data bands by writing identifying data within each band;

(c) setting aside one data band as an index band, wherein indexing data that identifies the information stored in each data band may be written;

(d) selectively writing desired data to a desired data band,

(e) writing in the index band a record of the data band where the desired data has been written; and (f) accessing and reading desired data by:

(1) using the index data band to quickly locate the particular data band where the desired data is stored, and

(2) directly accessing the desired data band in order to retrieve the desired data.

17. The method of Claim 16 wherein step (f) further includes writing the contents of the index band into a memory element as the optical disk is loaded into and initialized within said optical disk storage system, and determining where the desired data is located by electronically searching through said memory element.