News Column

Patent Issued for Dynamic Reduction of Tape Stain Accumulation on Tape Head Assembly across Multiple Environments

February 19, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- Oracle International Corporation (Redwood City, CA) has been issued patent number 8643974, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Partee, Charles C. (Lyons, CO); Boyer, Keith G. (Broomfield, CO).

This patent was filed on August 29, 2012 and was published online on February 4, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "The present invention generally relates to controlling the spacing of a tape head assembly (e.g., including one or more transducers such as a read transducer, a write transducer, or a read/write transducer) relative to a magnetic data storage tape and, more particularly, to controlling such spacing by reducing the buildup of tape stain on the tape head assembly over time.

"Tape drive manufacturers are constantly challenged to produce tape drives with larger storage capacity to meet market demands. One way to accomplish this objective is to increase the storage density in the magnetic layer of the tape. By increasing the storage density, the tape may have more tracks for a given area and each track may have more bits.

"An important factor affecting the accuracy of the read/write processes and the ability to support higher data densities is magnetic spacing. Generally, magnetic spacing is the distance between the magnetic layer on the tape where the information is recorded and the transducer(s) write and read data. Magnetic spacing is a first-order effect in all magnetic recording systems because increased magnetic spacing degrades write performance (to store data) and read performance (retrieving data) alike. Furthermore, magnetic spacing is a critical parameter because the amplitude of a playback signal decreases exponentially with increasing magnetic spacing. The decrease in amplitude caused by increased magnetic spacing may be referred to as Wallace spacing loss. Increased magnetic spacing increases the width of the read back pulse which leads to reduced data densities. The quality of the write operation also varies with spacing and decreased magnetic spacing improves the quality of the write operation.

"Magnetic spacing for a tape drive is typically set in the factory and can change during long term operation (e.g., long term movement of magnetic tape over the tape head assembly). After a sufficient period of time, a steady-state magnetic spacing develops. Magnetic spacing is generally designed to be in the range between 20-50 nm, depending upon product requirements. Generally, smaller magnetic spacing is capable of supporting higher data densities for a given read/write accuracy, while greater magnetic spacing is capable of supporting lower data densities for a given read/write accuracy. If a system is designed to run at high data densities, but the magnetic spacing is too large, an unacceptable drop in read/write accuracy will occur.

"One factor that increases magnetic spacing (and thus can lead to read/write accuracy loss) is the accumulation of 'tape stain' on the tape head assembly over time during operation of the tape drive. Tape stain formation is believed to be an electro-mechanical-chemical process in which an accumulation (e.g., amalgam) of lubrication products, head wear products, and other detritus produced from the head and tape (during the wear process that continues for the life of the tape drive) builds up on the tape head elements (e.g., shields, poles, substrates, reader elements, and/or the like), and can accumulate in differing amounts and at differing rates based on, among other factors, the particular environment in which the tape drive is operating (e.g., temperature, humidity, and/or the like). The accumulated tape stain increases the magnetic spacing between the head and the tape by physically pushing the tape further away from the head assembly. In some cases, tape stain can be electrically conductive which can cause shorts between film layers in the read transducer that are designed to be isolated and ultimately degrade read performance significantly. Regardless of whether or not it is electrically conductive, tape stain accumulated on the tape head assembly degrades overall performance and is a common cause for drive returns from customers.

"One manner of reducing tape stain is via use of a 'cleaning tape' having an abrasive surface that removes some of the stain. Upon accumulation of tape stain on a typical head assembly, drive software notes the performance degradation and requests that the tape library or tape operator loads the cleaning tape. In some situations, a cleaning tape can be periodically loaded even when performance degradation has not been noted. Although a common approach to mitigate the tape stain problem in the industry, use of cleaning tapes has significant disadvantages. For instance, use of cleaning tapes is often not completely effective in removing tape stain. Furthermore, cleaning tapes tend to decrease the overall mean time to failure of the head while increasing the cost of ownership of tape drives to customers. Still further, cleaning tapes merely mask the problem of tape stain accumulation by periodically and imperfectly removing the tape stain rather than eliminating or at least limiting the accumulation of the tape stain in the first place."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "Another manner of reducing tape stain accumulation in some environments is to apply a fixed voltage bias to certain elements in a tape head assembly. In the current manner, a fixed voltage bias is applied to the tape head elements irrespective of environment (e.g., temperature, humidity, and/or the like) so that the voltage bias is either beneficial (e.g., it eliminates or at least limits tape stain accumulation) or benign (e.g., it has no or little effect on tape stain accumulation). For instance, applying a voltage bias of 3V on one or more particular tape head assembly elements in a hot, humid environment may reduce tape stain accumulation while the same voltage bias applied to the same tape head assembly elements in a cold, dry environment may have little to no effect on tape stain accumulation. Recently, it has been discovered that different voltage bias levels may have differing effects on tape stain accumulation based upon the particular environment in which the tape drive is operating. Continuing with the above example, a voltage bias of 3V applied to particular tape head assembly elements may be highly effective in eliminating or at least limiting tape stain accumulation in a hot and humid environment while a different voltage bias (e.g., 1V) applied to particular tape head assembly elements may be highly effective in eliminating or at least limiting tape stain accumulation in a cold and dry environment. However, and as discussed above, current manners of reducing tape stain accumulation continue to apply the same voltage bias regardless of the particular environment in which the tape drive is being operated.

"Disclosed herein are systems and methods that broadly serve to detect or otherwise obtain one or more environmental conditions or variables of a tape drive and then dynamically apply one or more voltage biases (or bias differences) to one or more elements of the tape head assembly of the tape drive (or between elements) based on the detected/obtained environmental conditions to reduce tape stain accumulation and prolong tape head performance. Stated differently, the disclosed systems and methods are operable to apply voltage biases or differences to or between elements in the tape head assembly that are exposed to the magnetic tape (e.g., shields, poles, substrates, reader elements, and/or the like) at levels directly or substantially tied to the particular environmental conditions of the tape drive. For instance, detection of a first environment may result in a fixed voltage difference being held between two elements (e.g., between top and bottom poles) to limit tape stain accumulation in the first environment. As another example, detection of a second environment may result in one particular element being held at ground and a voltage being applied to another element relative to the grounded element to limit tape stain accumulation in the second environment. Environmental conditions can be determined/obtained and any appropriate voltage level(s) can be set before tape drive operation and/or environmental conditions can be dynamically determined/obtained and any appropriate voltage level(s) can be dynamically set during tape drive operation. Non-limiting examples of environmental conditions that may be detected/obtained include temperature, humidity, altitude, magnetic fields, tape type, tape movement direction relative to tape head elements, and/or the like.

"In one aspect, a method of voltage biasing one or more elements of a tape head assembly in a tape drive to limit tape stain accumulation on the tape head assembly includes obtaining a first set of one or more environmental variables of a tape drive that collectively make up a first environment of the tape drive; determining, based on the first environment, a first set of one or more voltage biases to be applied to a first set of one or more elements of a tape head assembly of the tape drive to limit the accumulation of tape stain on the tape head assembly during movement of magnetic tape relative to the tape head assembly in the first environment; and applying the determined first set of one or more voltage biases to the first set of one or more elements of the tape head assembly.

"In one arrangement, the method may include obtaining a second set of one or more environmental variables of a tape drive that collectively make up a second environment of the tape drive; determining, based on the second environment, a second set of one or more voltage biases to be applied to a second set of one or more elements of the tape head assembly to limit the accumulation of tape stain on the tape head assembly during movement of the magnetic tape relative to the tape head assembly in the second environment; and applying the determined second set of one or more voltage biases to the second set of one or more elements of the tape head assembly.

"In another arrangement, the obtaining may include receiving the one or more environmental variables from one or more sensors, where each sensor measures a physical property and converts the physical property into a corresponding signal, and where the environmental variables are represented by the corresponding signals. For instance, the determining may include accessing a database including a plurality of environmental variables and a plurality of tape head assembly elements and corresponding voltage biases to be applied to the tape head assembly elements to limit tape stain accumulation on the tape head assembly; and using the first set of one or more environmental variables to ascertain the first set of one or more voltage biases to be applied to the first set of one or more elements of the tape head assembly of the tape drive.

"In another aspect, a system for limiting tape stain accumulation on a tape head assembly during movement of magnetic tape over the tape head assembly includes a tape head assembly; a sensor that measures a physical property of an environment of the tape head assembly and converts the physical property into a corresponding signal; and a tape drive controller that receives the signal from the sensor and determines, based on the received signal, a voltage bias to be applied to an element of the tape head assembly to limit the accumulation of tape stain on the tape head assembly during movement of magnetic tape relative to the tape head assembly in the environment.

"In yet another aspect, a tape head assembly tape stain accumulation reduction system includes a processing module and a memory module logically connected to the processing module and comprising a set of computer readable instructions executable by the processing module to sense environmental variables affecting a degree to which tape stain accumulates on a tape head assembly of a tape drive, wherein the sensed environmental variables collectively make up a sensed environment; and apply, based on the sensed environment, a voltage bias to one or more elements of the tape head assembly to limit tape stain accumulation on the tape head assembly during movement of magnetic tape over the tape head assembly in the sensed environment. For instance, the memory module may include additional sets of computer readable instructions executable by the processing module to sense a plurality of additional environments of the tape drive; and apply, based on the plurality of additional sensed environments, voltage biases to one or more elements of the tape head assembly to limit tape stain accumulation on the tape head assembly during movement of magnetic tape over the tape head assembly in each of the plurality of additional sensed environments.

"Any of the embodiments, arrangements, or the like discussed herein may be used (either alone or in combination with other embodiments, arrangement, or the like) with any of the disclosed aspects. Merely introducing a feature in accordance with commonly accepted antecedent basis practice does not limit the corresponding feature to the singular. Any failure to use phrases such as 'at least one' does not limit the corresponding feature to the singular. Use of the phrase 'at least generally,' 'at least partially,' 'substantially' or the like in relation to a particular feature encompasses the corresponding characteristic and insubstantial variations thereof. Furthermore, a reference of a feature in conjunction with the phrase 'in one embodiment' does not limit the use of the feature to a single embodiment.

"In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following descriptions."

For the URL and additional information on this patent, see: Partee, Charles C.; Boyer, Keith G.. Dynamic Reduction of Tape Stain Accumulation on Tape Head Assembly across Multiple Environments. U.S. Patent Number 8643974, filed August 29, 2012, and published online on February 4, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=53&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=2644&f=G&l=50&co1=AND&d=PTXT&s1=20140204.PD.&OS=ISD/20140204&RS=ISD/20140204

Keywords for this news article include: Oracle International Corporation.

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Source: Journal of Engineering


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