Patent Application
20140140182
Data can be stored on several types of carrier media, such as hard disk drives, optical disks, and other forms of permanent or semi-permanent storage. Defects in carrier media result in unreliable behavior, poor performance, or data corruption. Testing for media defects can improve reliability in data storage systems.
An embodiment of the disclosure is a method of detecting and classifying at least one media defect. A periodic pattern is written to a medium to yield at least one waveform. The magnitude of the waveform is compared against a defect threshold to detect the presence or absence of media defects in the medium. When at least one defect is detected, a magnitude for each of at least two harmonics of the waveform is determined in the defect range. The magnitudes of the at least two harmonics are utilized to classify the defect.
It is to be understood that both the foregoing general description and the following detailed description are not necessarily restrictive of the disclosure. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the disclosure.
The embodiments of the disclosure may be better understood by those skilled in the art by reference to the accompanying figures in which:
Reference will now be made in detail to the embodiments disclosed, which are illustrated in the accompanying drawings.
The computing system 104 is configured for writing a periodic pattern to the test medium 102 to generate a waveform 120, as illustrated in
The computing system 104 is further configured for classifying the detected defect utilizing at least two harmonics of the waveform 120. In some embodiments, the two harmonics include, but are not limited to, a first harmonic and a third harmonic of the waveform 120. A harmonic is a component of the waveform 120 that has a frequency that is an integer multiple of the fundamental frequency. Accordingly, the first harmonic is a component of the waveform 120 at the fundamental frequency and the third harmonic is a component of the waveform 120 at three times the fundamental frequency, and so on.
The computing system 104 is configured for determining a magnitude of each harmonic over the defect range 122. The computing system 104 is further configured for determining a ratio 124 of the magnitudes of the two harmonics. As illustrated in
In an embodiment, the computing system 104 is configured to determine the ratio 124 of the magnitude of the third harmonic of the waveform 120 over the magnitude of the first harmonic of the waveform 120. The computing system 104 is configured to classify the defect as a TA defect when the ratio 124A is less than the classification threshold 126. The computing system 104 is further configured to classify the defect as a DLM defect when the ratio 1248 is not less than the classification threshold 126.
In another embodiment, the magnitude of the first harmonic and the third harmonic are determined in accordance with the following equation:
In the equation above, fn is a magnitude of the nth harmonic and x4T is the read back 4 T waveform at time instant k. The ratio 124 of the magnitudes of the two harmonics is determined in accordance with the following equation: ratio=f3/f1. The foregoing equations are included to illustrate an embodiment of the disclosure and are not intended to limit the disclosure in any way.
At step 202, a periodic pattern is written to the test medium 102 to yield at least one waveform 120. In some embodiments, the periodic pattern includes a 4 T pattern. At step 204, a magnitude of the waveform 120 is compared against a defect threshold to determine the presence or absence of a defect. In some embodiments, a defect is detected when the magnitude of the waveform 120 is less than the defect threshold. At step 206, magnitudes of at least two harmonics of the waveform 120 are determined over the defect range 122. In some embodiments, the two harmonics include a first harmonic of the waveform and a third harmonic of the wave form. At step 208, the defect is classified utilizing the magnitudes of the two harmonics. In some embodiments, a ratio 124 of the two harmonics is compared against a classification threshold 126 to determine the defect type. In some embodiments, the defect is classified as either a TA defect or a DLM defect based on whether the ratio 124 is less than the defect threshold 126 or not less than the defect threshold 126.
Another embodiment of a method 300 for detecting and classifying at least one media defect is illustrated in
At step 302, a periodic pattern is written to the test medium 102 to yield at least one waveform 120. At step 304, a magnitude of the waveform 120 is compared against a defect threshold to determine the presence or absence of a defect. At least one defect is detected when the magnitude of the waveform 120 is less than the defect threshold. At step 306, magnitudes of at least two harmonics of the waveform 120 are determined over the defect range 122. At step 308, a ratio 124 of the magnitudes of the two harmonics is determined. At step 310, the defect is classified by comparing the ratio 124 of the magnitudes of the two harmonics and a classification threshold 126 to determine the defect type.
In an embodiment, the ratio 124 determined at step 308 includes a ratio of the magnitude of the third harmonic of the waveform and the magnitude of the first harmonic of the waveform (i.e. ratio=f3/f1). At step 310, the defect is classified as either a TA defect when the ratio 124A is less than the classification threshold 126 (i.e. ratio<ClassT). The defect is alternatively classified as a DLM defect when the ratio 124B is not less than the defect threshold 126 (i.e. ratio≧ClassT).
It should be recognized that in some embodiments the various steps described throughout the present disclosure may be carried out by a single computing system or multiple computing systems. A computing system may include, but is not limited to, a personal computing system, mainframe computing system, workstation, image computer, parallel processor, or any other device known in the art. In general, the term “computing system” is broadly defined to encompass any device having one or more processors, which execute instructions from a memory medium.
Program instructions implementing methods, such as those manifested by embodiments described herein, may be transmitted over or stored on carrier medium. The carrier medium may be a transmission medium, such as, but not limited to, a wire, cable, or wireless transmission link. The carrier medium may also include a storage medium such as, but not limited to, a read-only memory, a random access memory, a magnetic or optical disk, or a magnetic tape.
Embodiments manifesting methods described herein may include storing results in a storage medium. After the results have been stored, the results can be accessed in the storage medium and used by any of the method or system embodiments described herein, formatted for display to a user, used by another software module, method, or system, etc. Furthermore, the results may be stored “permanently,” “semi-permanently,” temporarily, or for some period of time. For example, the storage medium may be random access memory (RAM), and the results may not necessarily persist indefinitely in the storage medium.
It is further contemplated that any embodiment of the disclosure manifested above as a system or method may include at least a portion of any other embodiment described herein. Those having skill in the art will appreciate that there are various embodiments by which systems and methods described herein can be effected, and that the implementation will vary with the context in which an embodiment of the disclosure deployed.
Furthermore, it is to be understood that the invention is defined by the appended claims. Although embodiments of this invention have been illustrated, it is apparent that various modifications may be made by those skilled in the art without departing from the scope and spirit of the disclosure.
