Dynamic magnetic information storage or retrieval – Checking record characteristics or modifying recording...
Reexamination Certificate
1998-08-26
2001-09-04
Sniezek, Andrew L. (Department: 2651)
Dynamic magnetic information storage or retrieval
Checking record characteristics or modifying recording...
C360S031000
Reexamination Certificate
active
06285518
ABSTRACT:
BACKGROUND
1. Field of the Invention
This invention pertains to the storage or backup of data using magnetic tape drives, and particularly to determining the wear of tape upon which data is stored/retrieved by such drives.
2. Related Art and Other Considerations
In magnetic recording on tape using a magnetic tape drive, relative motion between a head unit (typically with both a write element and a read element) and the tape causes a plurality of tracks of information to be transduced with respect to the tape. The magnetic tape is typically housed in a cartridge which is loaded into the tape drive. The tape extends between a cartridge supply reel and a cartridge take-up reel. The tape drive typically has a supply reel motor for rotating the cartridge supply reel and a take-up reel motor for rotating the cartridge take-up reel.
After the cartridge is loaded into the tape drive, the tape is extracted or loaded by mechanisms in the drive so that a segment of the tape is pulled from the cartridge and into a tape path that travels proximate the head unit. In some tape drives the extraction mechanisms take the form of tape guides which are mounted on trolleys. During the extraction operation, trolley motors move the trolleys along a predefined trolley path, so that the tape guides which surmount the trolleys displace the tape into the tape path as the trolleys travel along the trolley path. When the trolleys reach the full extent of travel along the trolley path, the tape is proximate the head unit. Thereafter the tape can be transported past the head unit, e.g., by activation of a capstan and/or the supply reel and take-up reel motors, depending upon the particular type of transport mechanisms employed. A capstanless tape drive, particularly a tape drive which utilizes helical scan recording, is shown in U.S. Pat. No. 5,602,694 for CAPSTANLESS HELICAL DRIVE SYSTEM, which is incorporated herein by reference.
As the tape is transported past the head unit, information can be transduced to or from the tape by the tape drive in recording and reading operations, respectively. When the recording and/or reading operations are concluded, and before the cartridge can be unloaded from the drive, the tape must be retracted for return to the interior of the cartridge. Tape retraction is essentially the reverse of the tape extraction procedure described above.
Because removable media such as that housed in a tape cartridge can be reused many times, the issue of when a magnetic tape is worn out assumes great importance to the end user. If a tape is near its end of life, data errors become more common and the possibility of a catastrophic loss increases. Manufacturers of computer tape drives typically specify tape durability in terms of a maximum allowable number of “passes” of the head unit over the tape. In the simplest case, writing data to a tape might involve only two passes over a given spot of the tape: a first pass in the forwarded direction to write the data and a second pass in the reverse direction to return to the beginning of the tape prior to an unload of the cartridge. In practice, issues of formatting, data rate mismatches, and error recovery cause the tape motion to be much more complex. Certain sections of the tape might be subject to many passes during a given operation while nearby sections see much less activity. Measuring tape wear under such real world circumstances has traditionally been impossible. As a compromise, many tape drive systems instead measure other factors such as the number of rewinds or load cycles which are only indirectly related to the number of passes.
For example, as previously marketed, the Exabyte Mammoth™ tape drive attempts to determine remaining tape life indirectly by recording how often certain types of motion have occurred on a tape. However, no record is made of where these motions have occurred on the tape. A relatively small number of start/stop motions occurring in a small area of tape can wear out that section, whereas a much larger number of similar motions will not do so if spread out across a large section of tape.
Other approaches for discerning tape life are provided in the prior art. U.S. Pat. No. 4,797,753 to Montgomery employs a separate calibration track whose output level and frequency content is monitored for degradation. U.S. Pat. No. 4,575,778 to Vogelgesang describes a mechanical counting wheel which is advanced one per use of a cassette. U.S. Pat. No. 4,485,674 to Ragle teaches that a so-called “stagger wrap” profile of a reel is unique for each rewind cycle, and thus can be used to indicate the number of cycles.
What is needed, therefore, and an object of the present invention, is a technique for effectively and efficiently indicating tape wear.
SUMMARY
Apparatus for transducing information relative to a recording media includes a transport system which transports the media whereby predefined locations on the media, known as media wear milestones, make a pass proximate a transducing element. A media wear monitoring system determines when a pass occurs with respect to each of the predetermined media wear milestones on the media, and in accordance with the determination provides an indication of media wear. The transport system includes a media takeup reel, the angular position of which is utilized by the media wear monitoring system to locate the media wear milestones. Preferably a position sensor on the media takeup reel is used to determine when a milestone has been crossed (without requiring that anything be recorded on the media at that location). Alternatively, sensors of other types, such as an idler wheel attached to a rotating sensor and drive by the media itself, can be employed.
The media wear monitoring system includes a media wear log stored in a memory. The media wear log includes an indication of a number of passes which has occurred with respect to each of the media wear milestones. In other words, each milestone has an associated counter. An array of such counters is recorded on the media as the media wear log at an appropriate location, and preferably next to the unload point.
Upon loading of the media into the apparatus the media wear monitoring system reads an initial version of the media wear log from the media into the memory. During transport of the media, the media wear monitoring system detects reaching of the media wear milestones and updates the media wear log by incrementing the indication of the number of passes for each of the media wear milestones. Upon unloading of the media from the apparatus, the media wear monitoring system writes an updated media wear log on the media, e.g., to a physical beginning of the media.
In one embodiment, the media wear milestones are essentially uniformly distributed along a linear length of the media. In another embodiment, the media wear milestones are concentrated more closely together at a beginning of the media, e.g., in accordance with a square law distribution.
In one mode of the invention, the media wear monitoring system generates a signal indicative of worn media when a predetermined number of passes has occurred for one of the media wear milestones on the media. In another mode of the invention, the media wear monitoring system generates a signal indicative of extent of wear of the media. The signal generated by the media wear monitoring system is applied to an output device, such as a display device.
REFERENCES:
patent: 4485674 (1984-12-01), Ragle
patent: 4575778 (1986-03-01), Vogelgesang
patent: 4797753 (1989-01-01), Montgomery
patent: 5426355 (1995-06-01), Zweighaft
patent: 5602694 (1997-02-01), Miles et al.
patent: 5712539 (1998-01-01), Zweighaft et al.
patent: 5734518 (1998-03-01), Hughes
patent: 5901007 (1999-05-01), Oguro et al.
patent: 5926777 (1999-07-01), Vink et al.
Exabyte Corporation
Nixon & Vanderhye P.C.
Sniezek Andrew L.
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