Error detection/correction and fault detection/recovery – Pulse or data error handling – Error count or rate
Reexamination Certificate
2000-01-18
2001-11-13
Chung, Phung M. (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Error count or rate
Reexamination Certificate
active
06317850
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to disk drives. More particularly, the present invention relates to computing an error rate measurement in a disk drive by weighting data-recovery procedures.
2, Description of the Prior Art
The error rate of a disk drive provides useful information about the drive's performance, for example, how to improve performance by calibrating the drive or how likely the drive will fail in the future. A conventional method for estimating the error rate is to divide the number of addressable locations with errors by the total number of addressable locations:
Error Rate=Addressable locations With Errors/Total Addressable locations. An addressable location is deemed to have errors if it cannot be successfully recovered using conventional sequence detection and error correction code (ECC) techniques during a read operation. There are several reasons an addressable location may not be successfully recovered during a read operation. For example, the addressable location may have an error associated with the media (e.g., media defects, high-fly writes, off-track writes, etc.) or the signal processing circuitry (e.g., the head, preamp, gain control, equalizers, etc.).
The conventional method of estimating the error rate using the above equation may not be reliable for certain applications such as calibrating the drive or predicting drive failure. For example, the conventional method of estimating the error rate does not differentiate between errors associated with the media and errors associated with the signal processing circuitry. Therefore, it may not be reliable to calibrate components in the signal processing circuitry using the conventional method of estimating the error rate. Similarly, the conventional method of estimating the error rate may not be reliable for predicting drive failure because the errors associated with the media and the errors associated with signal processing circuitry typically influence the error rate in different ways. For example, the media may degrade slower than the signal processing circuitry which can lead to errors in predicting drive failure. Further, particular signal processing components may degrade faster than others which is not taken into account in the conventional method of estimating the error rate.
There is, therefore, a need to generate a more reliable error rate measurement in a disk drive for use in applications such as drive calibration or drive failure prediction.
SUMMARY OF THE INVENTION
The present invention may be regarded as a disk drive comprising a disk including a plurality of addressable locations containing stored data, and signal processing circuitry comprising reading means responsive to the stored data for producing a read signal, and means responsive to the read signal for producing decoded data that is subject to errors. A control system, responsive to the decoded data, computes an error rate measurement by performing a first data-recovery procedure conducted under conditions providing for increasing the probability of achieving a first successful data-recovery step, and by performing a second data-recovery procedure conducted under conditions providing for increasing the probability of achieving a second successful data-recovery step. The control system accumulates a first accumulated value representing occurrences of the first successful data recovery step and accumulates a second accumulated value representing occurrences of the second successful data recovery step. The control system weights the first accumulated value by a first weight to generate a first weighted value, and weights the second accumulated value by a second weight different than the first weight to generate a second weighted value. The control system computes the error rate measurement by combining the first and second accumulated values and the first and second weighted values.
The present invention may also be regarded as a method of computing an error rate measurement in a disk drive comprising a disk including a plurality of addressable locations containing stored data and signal processing circuitry comprising reading means responsive to the stored data for producing a read signal and means responsive to the read signal for producing decoded data that is subject to errors. A first data-recovery procedure is performed on the decoded data conducted under conditions providing for increasing the probability of achieving a first successful data recovery step, and a second data-recovery procedure is performed on the decoded data conducted under conditions providing for increasing the probability of achieving a second successful data recovery step. A first accumulated value is generated representing occurrences of the first successful data recovery step, and a second accumulated value is generated representing occurrences of the second successful data recovery step. The first accumulated value is weighted by a first weight to generate a first weighted value, and the second accumulated value is weighted by a second weight different than the first weight to generate a second weighted value. An error rate measurement is computed by combining the first and second accumulated values and the first and second weighted values.
REFERENCES:
patent: 5889784 (1999-03-01), Rogers
Chung Phung M.
Shara Milad G
Western Digital Technologies Inc.
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