Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1997-12-29
2001-02-06
Sniezek, Andrew L. (Department: 2753)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S075000
Reexamination Certificate
active
06185063
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to data storage devices, and more particularly to methods and apparatus that provide for more efficient use of the recording space available on a storage medium and an increase in the data storage capability of a storage device.
BACKGROUND OF THE INVENTION
Data storage devices are commonly used in computer systems to store large amounts of data. Certain types of data storage devices, such as tape drives, are normally used to provide archival storage of large amounts of data. Other types of data storage devices, such as disk drives, are typically used in workstations, personal computers, laptops and mainframe computer systems to store large amounts of data that can be quickly stored and retrieved.
Each of these exemplary data storage devices, i.e., the tape drive and disk drive, utilizes a data storage medium on which information is stored in the form of data. The storage medium in a tape drive is typically a magnetic tape, and the storage device in a disk drive is typically a magnetic disk, although other types of drives use other types of disks (e.g., optical disks). A tape drive normally comprises a servoing system configured to move the tape past one or more transducers arranged to read/write data on the tape. A disk drive generally comprises at least one magnetic disk that is rotated about an axis by a spindle motor and positioned to be accessed by one or more transducers. The surfaces of both the tape and the disk are typically divided into a series of data tracks. The data tracks on a tape can take several different shapes, including, for example, helical, arcuate and linear shapes. The data tracks on a disk usually extend circumferentially, typically in a concentric pattern, around the disk. Each data track, on either a magnetic tape or magnetic disk, stores data in the form of magnetic transitions on a recordable surface of the tape/disk. For example, each transition can represent a bit of information.
It is expected that users of disk drives and tape drives will place ever greater demands on manufacturers with regard to the amount of data that can be stored on and retrieved from a data storage device. This is especially true for modern software programs, which include graphics and other data structures that dramatically increase the amount of data that needs to be accessed. In addition, the rapid growth and the use of servers on computer networks requires large storage capabilities to accommodate the data needs of a larger number of users on the network who utilize network based servers and/or shared resources.
In recent years, the trend has been to design and build data storage devices that are capable of supporting these increasing needs. For example, one trend has been to provide disks that can support more information (often in a more compact size), and that can be operated at higher rotational velocities to increase data read and write rates. One consequence, however, of these improvements is that the data density on the recordable surface of the disks/tapes and the associated speeds of the disks/tapes are approaching the perceivable limits of conventional transducers and associated circuitry to rapidly and accurately read/write the closely spaced, fast-moving magnetic transitions required by such storage devices.
By way of example, in order to meet the data reading requirements in a conventional disk drive, a magnetoresistive (MR) transducer is typically used. The MR transducer is coupled to an electronic read channel that implements signal processing techniques, such as partial response maximum likelihood (PRML) detection. The MR transducer is configured to sense the magnetic transitions on the disk drive, and to produce a corresponding change in electrical resistance as a function of a change in magnetic flux on the disk. The MR transducer is coupled to an electronic circuit, for example, a pre-amplifier that detects the resistance changes in the MR transducer and generates one or more corresponding electrical signals that vary in time as a function of the resistance. Thus, the typical pre-amplifier outputs a signal that corresponds to the data recorded as magnetic transitions on the disk surface. This signal is then supplied to the remaining portions of the read channel which essentially extract/interpret the data represented within the signal.
A write channel is basically the opposite of the read channel, in that an electrical signal representing data is provided to a write head which is configured to affect the magnetic flux on the recordable surface and record the data as transitions therein.
However, because of differences in fabrication and manufacturing processes, a typical write head is much larger (e.g., twice as large or larger) than a read head equipped with an MR transducer. By way of example, it is possible given current technology to manufacture a read head that is narrow enough to read 25,000 tracks per inch (TPI). Write heads narrow enough to write 25,000 TPI are not known to date.
Thus, there is a need for methods and apparatus that effectively take advantage of the higher TPI capability of a narrow read head while also using a significantly wider write head.
SUMMARY OF THE INVENTION
The present invention provides methods and apparatus that allow overlapping data tracks to be stored on a recordable surface of a storage medium. The methods and apparatus provide differing data track storage formats, each of which advantageously increases the track pitch to take advantage of a read transducer that is narrower than a corresponding write transducer. This is accomplished by selectively overlapping wide data tracks during a write operation, while leaving enough of each data track to be subsequently read by the narrower read transducer during a read operation.
In accordance with one aspect of the present invention, a “wide-write and narrow-read” method is provided for use in a disk drive having a write head and a narrower read head. The method includes writing a plurality of data tracks on an information storage disk with a write head, such that a subsequently written data track partially overlaps a previously written data track. The method then includes reading a non-overlapped portion of at least one of the plurality of data tracks with a read head.
In accordance with another aspect of the present invention, a method is provided for writing a plurality of tracks of data on, and reading the plurality of tracks of data from, a storage medium. The method includes writing a first track of data along a first path, the first track of data having an initial width, and writing a second track of data along a second path, the second track of data having the same initial width, as the first track of data. The second path substantially follows the same direction as the first path, however a portion of the second track overlaps a portion the first track of data. Consequently, there is provided a reduced first track of data having a reduced width that is narrower than the initial width. The method subsequently includes reading at least a portion of the reduced first track of data and at least a portion of the second track of data with a read transducer. In certain embodiments this method further includes writing a third track of data along a third path and a fourth track of data along a fourth path such that the third and fourth paths substantially follow the same direction of the second path, and a portion of the fourth track of data overwrites a portion the third track of data. As a result, a third track of data that has a reduced width is provided. However, even after writing the third track of data the second track of data still has an initial width. In certain embodiments, the storage medium is an information storage disk, while in other embodiments, the storage medium is an information storage tape.
The above stated needs are also met by an apparatus, in accordance with one aspect of the present invention, for use in a data storage device in writing data to a storage medium via a write transducer, and re
Dempster Shawn B.
Heller III Edward P.
Olson Jonathan E.
Seagate Technology LLC
Sniezek Andrew L.
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