The assignee for this patent application is
Reporters obtained the following quote from the background information supplied by the inventors: "This invention relates to apparatus and methods for reading and writing data on storage media such as magnetic tape.
"In most tape drives, magnetic tape is passed between spools and over guiding elements such as rollers in order to direct the magnetic tape across a read/write head. The read/write head typically includes a number of write elements to write tracks on the magnetic tape, and an equivalent number of read elements to read back data from the magnetic tape as it is written. This allows the written data to be verified as it is written. In order to provide some leeway when reading back data, the read elements are typically narrower than the write elements, and thus narrower than the tracks they are reading back. This allows the read elements to read back data even if they are not exactly centered over the written tracks. However, if the misalignment between the read elements and the center of the written tracks is enough, a point may be reached where the read elements can no longer accurately read back the data.
"The misalignment between the read elements and written tracks, which is generally caused by angular misalignment of the read/write head relative to the magnetic tape, is typically referred to as 'skew.' The greater angular misalignment of the read/write head relative to the tape, the greater the skew. As alluded to above, if the skew is large enough, the read elements may no longer be able to read back data from the magnetic tape.
"In some tape drives, such as some LTO tape drives, the angle of the read/write head can be manually adjusted relative to the tape in order to minimize the skew. Unfortunately, shifts in the tape stack can cause the skew readings to change as the magnetic tape traverses across the head. Thus, adjusting the angle of the read/write head or the magnetic tape to minimize the skew can be like hitting a moving target. That is, a technician may adjust the angle to minimize the skew only to find that the skew later increases due to variations in the tape stack. Thus, a technician may have difficulty finding an optimal angular position for the tape head relative to the magnetic tape.
"In view of the foregoing, what are needed are apparatus and methods for adjusting skew in the presence of tape motion. Ideally, such an apparatus and method will enable a technician to easily adjust the angular position of a tape head relative to the magnetic tape even while the tape is in motion."
In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventors' summary information for this patent application: "The invention has been developed in response to the present state of the art and, in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available apparatus and methods. Accordingly, the invention has been developed to provide apparatus and methods for more accurately adjusting skew in the presence of tape motion. The features and advantages of the invention will become more fully apparent from the following description and appended claims, or may be learned by practice of the invention as set forth hereinafter.
"Consistent with the foregoing, a method for accurately adjusting skew in the presence of tape motion is disclosed herein. In one embodiment, such a method includes performing a calibration run of magnetic tape in a tape drive. During the calibration run, the method records skew readings at selected intervals. The method then finds a range associated with the skew readings, such as by finding a high and low skew reading. The method then finds a center point of the range, and a difference between the center point and a desired center point. The method then applies the difference to each recorded skew reading to generate a target skew reading for each recorded skew reading. The method generates a skew error signal that reflects the difference between each recorded skew reading and each corresponding target skew reading. The skew error signal will generally be consistent even as the tape moves, thereby allowing a technician to easily adjust and optimize the skew.
"A corresponding apparatus and computer program product are also disclosed and claimed herein.
BRIEF DESCRIPTION OF THE DRAWINGS
"In order that the advantages of the invention will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through use of the accompanying drawings, in which:
"FIG. 1 is a perspective cutaway view of one embodiment of a tape drive configured to read/write data on magnetic tape;
"FIG. 2 is a high-level view of a read/write head comprising multiple write elements and multiple read elements configured to write data tracks and read back data tracks on magnetic tape;
"FIG. 3A is a high-level diagram showing a read element substantially centered over a written track;
"FIG. 3B is a high-level diagram showing misalignment of a read element over a written track;
"FIG. 4 is a process flow diagram showing one embodiment of a method for adjusting skew in the presence of tape motion;
"FIG. 5 is a table showing an example of skew readings and error signals prior to and after making adjustments to the skew;
"FIG. 6A is a graph showing an example of skew readings for a tape drive prior to adjusting the skew;
"FIG. 6B is a graph showing an example of skew readings for a tape drive after adjusting the skew using a method in accordance with the invention; and
"FIG. 7 is a high-level block diagram showing various modules that may be included in an apparatus in accordance with the invention."
For more information, see this patent application: Inch,
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