WO2001018804A1

WO2001018804A1 - Disk drive with multiple heads for reduced track access time

Info

Publication number: WO2001018804A1
Application number: PCT/US2000/024566
Authority: WO
Inventors: D. Christopher Ohly
Original assignee: Ohly D Christopher
Priority date: 1999-09-09
Filing date: 2000-09-08
Publication date: 2001-03-15
Also published as: WO2001018804B1; WO2001018804A9; AU7575700A

Abstract

A drive such as a hard disk drive allows access to multiple tracks on the disk simultaneously. A first embodiment has multiple fixed heads (19), one for each track (15). A second embodiment has several independently movable arms (61A-61D) with heads (19A-19D). Each arm (61A-61D) is movable over a portion (57A-57D) of the disk (7) such that all of the arms (61A-61D) together cover the entire disk (7). A controller (23/25 and 53/55) allows some or all of the heads (19/19A-19D) to perform reading or writing operations concurrently.

Description

DISK DRIVE WITH MULTIPLE HEADS FOR REDUCED TRACK ACCESS

TIME

Background of the Invention

The present invention is directed to a persistent mass storage device, such as a hard disk drive, and more particularly to a mass storage device that provides rapid access to data stored thereon.

Hard disk drives are used on many kinds of computing devices and have been standard equipment on microcomputers since at least the IBM PC XT of the early 1980's. Hard disk drives function as persistent mass storage - persistent because they retain their data when the power is turned off, and mass because of their enormous capacity, which is now measured in gigabytes or tens of gigabytes.

As persistent mass storage, a hard disk drive performs several functions in a microcomputer. The computer's operating system can be, and usually is, booted from the hard disk drive. Operating systems outgrew floppy disks more than a decade ago, and while the technology exists to boot from a removable mass storage medium such as a CD-ROM, the speed is unacceptable to most users. The hard disk drive also stores applications and shared resources such as typefaces. In addition, most users rely on their hard disk drives to store user-created files such as word-processing documents, at least between backups. Finally, some operating systems, such as Microsoft Windows, allow hard-disk space to be used as virtual memory when physical RAM runs out.

A hard disk drive includes one or more platters, typically two to four, on a spindle turned by a drive motor. In most drives, each platter is double-sided; that is, it has magnetic or magneto-resistive recording material coated on both surfaces. To read and write data, one read-write head is provided per surface, or two per platter. The heads are mounted on arms, which are turned by an actuator motor (which is typically a servo motor, but can alternatively be a stepper motor) to access any part of the recording area of each surface. The operating system logically formats the surface onto multiple consecutive tracks, each divided into sectors of, e.g., 512 bytes. The sectors are grouped into clusters of, e.g., 8 sectors or 4 kilobytes each. The specifics vary with each operating system.

Controller electronics provide an interface between the read-write heads and the drive and actuator motors, on one hand, and the rest of the computer, on the other. Many kinds of controller electronics, such as IDE and SCSI, are widely used for controlling hard disk drives. The controller electronics can be integrated into the disk, as is the case with IDE, or can be provided on a separate card or circuitry on the motherboard, as is the case with SCSI.

Data are written thus. The drive has some sort of indexing scheme implemented by the operating system, such as the FAT (file allocation table) in DOS, to indicate which clusters are available for writing. The operating system chooses the clusters to hold the data and controls the drive motor and the actuator motor so that the read- write heads access each of the chosen clusters in turn.

Data are read similarly. The operating system uses the above-noted indexing scheme to determine which clusters hold a file desired to be read and controls the drive motor and the actuator motor so that the read-write heads access each of the clusters in turn.

The hard disk drive also acts as a serious bottleneck. The speed with which data are written to a disk drive or read from is determined by a number of variables. In part, the speed of such data transfer is limited by the rotational speed of the rotating magnetic or magneto-resistive disks which form a part of the disk drive. The rotational speed of such disks, as well as the speed with which particular tracks are located, is most significantly limited by the time consumed by the movement of the actuator motor to move the head across the surface of the rotating disks. While the distance traveled is small, the physical transit of such movable electromagnetic devices to access data on disk drives occurs in milliseconds. In contrast, access to data stored in random access memory occurs in nanoseconds.

Whether the operating system is being booted, an application is being loaded, or a document is being read or written, the hard disk drive handles the data much more slowly than do the other components of the computer, such as the CPU or the

RAM. Newer hard disk drives provide modest improvements through faster rotation. However, the speed of the actuator motor remains a problem. Also, the speed of the drive and actuator motors must be traded off against the severe constraints of accuracy due to ever increasing storage density. While the bottleneck could be removed by replacing the hard disk drive with static RAM, the price would be prohibitive.

Summary of the Invention

It will be readily apparent that a need exists in the art to remove the above- noted bottleneck at a reasonable cost. Therefore, it is a primary object of the invention to provide a hard disk drive or similar drive with reduced access time. It is another object of the invention to provide a hard disk drive or similar drive whose access time is not limited by the time required for the actuator motor to move the read-write heads across the surface of a platter.

It is yet another object of the invention to speed up access by accessing multiple clusters in a hard disk drive or similar drive simultaneously. To achieve the above and other objects, the present invention is directed to a drive in which it is not required to move the read-write heads across the entire surface. Instead, multiple read-write heads are provided for each surface, each head accessing only a part of the surface. Such an arrangement not only reduces the time required for the actuator motor to access a desired cluster, but also allows multiple clusters to be accessed simultaneously.

In a first embodiment, the read-write heads are fixed in position, and a number of read-write heads equal to the number of tracks on each surface is provided. No actuator motor is required at all.

The first embodiment provides for such increased disk drive speed through replacement of the physical actuator that provides for movement of the movable electromagnetic device across a rotating magnetic or magneto-resistive disk, with a stationery device on which an appropriate number of electro-magnetic read-write heads are located. In particular, multiple surface-mounted miniature electro-magnetic read-write heads are spaced apart from one another far enough to avoid any residual magnetic effects, as hysterisis, which might be occasioned by the rapid firing of such heads in proximity with another. Such heads are placed either in a straight line across a radius of a circular printed circuit board, or diagonally or otherwise across such a circular printed circuit board, in several locations (i.e., several radii, diagonals or other locations) on the circuit board, for optimum efficiency in use of space, electronic placement and magnetic interaction.

Printed circuit wiring connects each such head to an electronic controller to be located at an appropriate location on the circuit board, such as along the outside edge or circumference of the printed circuit board. One such controller may be used for all or part of such line of heads, or for several such lines or clusters of heads, and all necessary controllers may be linked and controlled, in turn, by a further, larger, controller, located either on the printed circuit board or on another board adjacent to the circular board.

A sufficient number of lines or clusters of heads and their respective controllers are located on the printed circuit board so that each track on a rotating magnetic or magneto-resistive disk may be addressed separately by its own head. The result is that no physical movement will be required to access any single track. Instead, each track is accessed by its own electro-magnetic head.

Since no physical movement of any actuator arm is required, operating system software can be modified or developed to control the firing of individual heads to read or write as required, sequentially, simultaneously, or both.

The printed circuit board described above is placed adjacent to a rotating magnetic or magneto-resistive disk, much as a mechanical actuator is presently located. Such printed circuit boards may be manufactured with heads on one or both sides, so that a single printed circuit board may be manufactured for location between two rotating magnetic or magneto-resistive disks, and so that, as with current disk drives, several such rotating magnetic or magneto-resistive disks may be stacked. Because no physical movement of any actuator is involved, at least to the extent that electro-magnetic effects of simultaneous firing of individual heads will permit, several heads may be accessed simultaneously by the operating system, greatly multiplying the speed increase which will result.

Likewise, because no physical movement of any actuator is involved, and because the physical distance between a rotating magnetic or magneto-resistive disk and the circular printed circuit board described above remains constant, it may be expected that the useful life of disk drives will increase, since there will be a smaller likelihood of a head crash, i.e., contact between a rotating disk and an adjacent surface. Similarly, since the physical distance between a rotating magnetic or magricto-resistive disk and the circular printed circuit board described above remains constant, it may be expected that the rotational speed of the rotating magnetic or magneto-resistive disk may also be increased, again increasing the rate of data transfer.

While it is anticipated that, at least initially, manufacturing costs of the invention may be larger than costs associated with conventional disk drives, given the nature of the technology involved and its likely widespread acceptance and utility, it is likely that manufacturing techniques will be developed that will quickly reduce the price of the invention.

In a second embodiment, multiple arms are provided, each bearing a read- write head for each of the surfaces. Each arm is driven by its actuator motor across only a portion of each surface; for example, if there are four arms, each arm is driven across only one-quarter of the surface. While the actuator motors are not eliminated, the part of the access time attributed to movement is the actuator arm is cut by a factor four, and up to four clusters on each surface can be accessed simultaneously. Any suitable controller technology can be adapted for use with either embodiment, e.g., IDE or SCSI. Also, either embodiment can be adapted for use with a removable disk cartridge drive, e.g., an Iomega Zip drive or a Syquest EZ drive.

Brief Description of the Drawings

Preferred embodiments of the present invention will be set forth in detail with reference to the drawings, in which:

Fig. 1 is a top view of a drive according to a first embodiment of the present invention;

Fig. 2 is a sectional view taken along lines II-II of Fig. 1 ; and

Fig. 3 is a top view of a drive according to a second embodiment of the present invention.

Detailed Description of the Preferred Embodiments

Preferred embodiments of the present invention will now be set forth in detail with reference to the drawings, in which like reference numerals refer to like components throughout. Each embodiment will be shown for simplicity as having one platter with one surface; those skilled in the art who have reviewed the present disclosure will readily be able to extend both embodiments to multiple platters having one or two recording surfaces each. Also, whenever a technology is not specified, it will be understood that technologies from the prior art can be adapted for use with the present invention. Figs. 1 and 2 show a view of the first embodiment of the present invention.

The drive 1 includes an enclosure 3 defining a space 5. A disk or platter 7 having a surface or surfaces 9 (of which only one is shown for simplicity) with magnetic recording material thereon, as in the prior art, is mounted in the space 5 on a spindle 11 which is spun by a drive motor 13. Each surface 9 has a plurality of tracks 15 formed therein.

Adjacent to the surface 9 of the platter 7 is a stationary support member 17 holding multiple stationary read- write heads 19, one for each track 15. The heads 19 are arranged in a two-dimensional array, such as a rectilinear grid or a radial array, to accommodate all of the needed heads 19 on the support member 17. The support member 17 can partially or completely cover the platter 7.

Each head 19 is electronically connected by a lead 21, which can be formed on the support member 17 by conventional printed-circuit techniques, to controller electronics 23. The controller electronics 23 can be adapted from conventional controller electronics (e.g., SCSI or IDE) to control the heads 19. In particular, the controller electronics 23 can include multiple controllers 25 for controlling multiple heads 19 to read or write simultaneously, e.g., one controller 25 for each row of heads 19. Another lead 27 allows the controller electronics 23 to control the drive motor 13 as desired, e.g., to power down in sleep mode to conserve power. The drive 1 according to the first embodiment can speed up disk access in at least the following ways. First, because the heads 19 are stationary and there is a head 19 for each track 15, any track 15 on the disk 7 can be accessed practically instanteously, with no need to move any head 19 by an actuator motor. Second, the use of multiple controllers 25 to control some or all of the heads 19 to read or write simultaneously allows faster reading or writing.

Fig. 3 shows a view of a second embodiment of the present invention. In the drive 51 according to the second embodiment, the enclosure 3, the space 5, the platter 7, the surface 9, the spindle 11, the drive motor 13 and the tracks 15 are as described above. The controller electronics 53 and the individual controllers 55 are modified as needed from the controller electronics 23 and the controllers 25 of the first embodiment.

The surface 9 is divided into four zones 57A, 57B, 57C, 57D. The four zones 57A-57D together comprise all of the tracks 15. The surface 9 need not be physically divided into the four zones 57A-57D, as long as the surface 9 is logically divided. Four actuator motors 59A, 59B, 59C, 59D drive arms 61 A, 61B, 61C, 61D, each with a read-write head 19A, 19B, 19C, 19D. None of the actuator motors 59A-59D drives its arm 61A-61D across the entire surface 9. Instead, each of the actuator motors 59A-59D drives its arm across a corresponding zone 57A-57D, so that every track 15 on the surface 9 is accessible by one of the heads 19A-19D. The controllers 55 are connected to the actuator motors 59A-59D and the heads 19A-19D by leads 63, of which only two are shown for simplicity, both to transmit data and to actuate the actuator motors 59A-59D.

The drive 51 according to the second embodiment can speed up disk access in at least the following ways. First, while the actuator motors 59A-59D are not eliminated, each actuator motor 59A-59D propels its corresponding head 19A-19D over only one-quarter of the distance required in the prior art. Therefore, the maximum time to access any track 15 is only one-quarter of the time required in the prior art. Second, the use of multiple controllers 55 to control some or all of the heads 19A- 19D to read or write simultaneously allows faster reading or writing.

In conventional drives, operating systems such as DOS typically write a file in consecutive clusters on one or more tracks. According to either of the embodiments of the present invention, different arrangements can be used to speed reading and writing. Those skilled in the art who have reviewed the present disclosure will readily appreciate the modifications which can be made to operating systems to accommodate such arrangements.

While two prefeπed embodiments have been set forth above, those skilled in the art who have reviewed the present disclosure will readily appreciate that other embodiments can be realized within the scope of the invention. For example, while the second embodiment has been taught as having actuator motors, head on rails, such as those which are known for use with magneto-optical drives, can be used instead. Also, either embodiment can be adapted for use with fixed disk drives or removable disk drives, such as cartridge drives, and for magnetic or other media, such as optical media. In addition, while both embodiments have been taught as having read-write heads, the invention can easily be adapted for use with read-only media. Therefore, the present invention should be construed as limited only by the appended claims.

Claims

I claim:

1. A data storage device comprising:

(a) a data storage medium having a plurality of tracks for storing data;

(b) a fixed member having a plurality of fixed heads for accessing the tracks, one of the heads being provided for each of the tracks; and

(c) moving means for moving the medium relative to the fixed member such that the tracks move relative to the fixed heads and each head accesses a corresponding one of the tracks.

2. The data storage device of claim 1, wherein the medium is a magnetic medium.

3. The data storage device of claim 2, wherein the data storage medium is a fixed hard disk.

4. The data storage device of claim 3, wherein the tracks are circular and are aπanged concentrically on the disk.

5. The data storage device of claim 4, wherein: the disk is mounted on a spindle; and the moving means comprises a motor for turning the disk through the spindle.

6. The data storage device of claim 1, further comprising controller means for controlling at least some of the heads to access corresponding ones of the tracks concurrently.

7. A data storage device comprising:

(a) a data storage medium having a plurality of tracks for storing data;

(b) a plurality of independently movable members having a plurality of heads for accessing the tracks, each of the plurality of movable members for moving at least one of the heads over some of the tracks such that the plurality of heads together are capable of accessing all of the tracks; and

(c) moving means for moving the medium relative to the plurality of movable members such that the tracks move relative to the heads and each head accesses a coπesponding one of the tracks.

8. The data storage device of claim 7, wherein the medium is a magnetic medium.

9. The data storage device of claim 8, wherein the data storage medium is a fixed hard disk.

10. The data storage device of claim 9, wherein the tracks are circular and are arranged concentrically on the disk.

11. The data storage device of claim 10, wherein: the disk is mounted on a spindle; and the moving means comprises a motor for turning the disk through the spindle.

12. The data storage device of claim 7, further comprising controller means for controlling at least some of the heads to access corresponding ones of the tracks concuπently.

13. The data storage device of claim 7, wherein each of the plurality of movable members comprises an actuator motor.

14. A device for accessing a data storage medium, the medium having a plurality of tracks for storing data, the device comprising:

(a) an enclosure defining a space in which the medium is disposed when the medium is to be accessed;

15. The device of claim 4, wherein: the medium is a disk; and the moving means comprises: a spindle for mounting the disk; and a motor for turning the disk through the spindle.

16. The device of claim 14, further comprising controller means for controlling at least some of the heads to access corresponding ones of the tracks concurrently.

17. A device for accessing a data storage medium, the medium having a plurality of tracks for storing data, the device comprising: (a) an enclosure defining a space in which the medium is disclosed when the medium is to be accessed;

(c) moving means for moving the medium relative to the plurality of movable members such that the tracks move relative to the heads and each head accesses a corresponding one of the tracks.

18. The device of claim 17, wherein: the medium is a disk; and the moving means comprises: a spindle for mounting the disk; and a motor for turning the disk through the spindle.

19. The device of claim 17, further comprising controller means for controlling at least some of the heads to access corresponding ones of the tracks concuπently.

20. The device of claim 17, wherein each of the plurality of movable members comprises an actuator motor.