Technique for reassigning data sector by detecting soft defect

Details Technique for reassigning data sector by detecting soft defect Technique for reassigning data sector by detecting soft defect

1998-07-27

2001-05-29

Faber, Alan T. (Department: 2651)

Dynamic magnetic information storage or retrieval

General processing of a digital signal

Data verification

Reexamination Certificate

active

06239931

ABSTRACT:

CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. § 119 from an application for METHOD FOR REASSIGNING DATA SECTOR BY DETECTING SOFT DEFECT earlier filed in the Korean Industrial Property Office on the Jul. 26
th
1997 and there duly assigned Serial No. 35381/1997.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data sector reassigning technique in a hard disk drive, and a disk surface using SMART (Self Monitoring Analysis & Reporting Technology).
2. Description of the Related Art
In a hard disk drive used as an auxiliary memory device of a computer system, growable soft defects are beforehand detected from a data sector, and another normal data sector is reassigned to substitute for the defective data sector. This is called automatic reassignment. Detection of the growable soft defects is performed mainly by varying an ECC (Error Correction Code) correction capability. In this method, data is read with a low ECC correction capability in an early stage. If an ECC error is generated during the data read, it is determined whether the error is recovered by an error recovery routine. If the error is not recovered, the ECC correction capability is set to a maximum and the data is re-read. Then, if the data is read without any error, the read data is written in a remapped, that is, reassigned data sector.
However, the above method has the following drawbacks. Data sectors having growable soft defects cannot be accurately estimated because the ECC correction capability is set to a maximum without consideration of head performance or disk characteristics. Hence, too many data sectors unnecessarily turn out defective. That is, assuming that a normal ECC correction capability is 1, a maximum ECC correction capability is 2, and an error rate increases at the ECC correction capability of 1, the ECC correction capability is set to 2 according to the above method. As a result, data sectors having soft defects unlikely to grow are determined to be defective sectors, lowering the total performance of the drive.
The following patents each disclose features in common with the present invention but do not teach or suggest the technique for reassigning a data sector by detecting a soft defect as in the present invention: U.S. Pat. No. 5,237,553 to Fukushima et al, entitled Data Recording And Reproducing Apparatus Having A Plurality Of Operating Modes, and U.S. Pat. No. 5,150,050 to Genheimer et al., entitled Adaptive Variable Threshold Qualification Level Circuit For Signal Processing In Disk Drives.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a technique for reassigning a data sector by accurately detecting only growable soft defects, and changing an ECC correction capability according to an error rate varied with head/disk assembly characteristics.
To achieve the above object, there is provided a method of reassigning a data sector by detecting a soft defect in a hard disk drive having a plurality of data sectors and an error correction capability. In the data sector reassigning method, an error rate is calculated during a data read, a soft defect is detected by varying the error correction capability according to the calculated error rate, a read error of the detected soft defect is recovered by setting the error correction capability to a maximum level if the read error is not recovered, and a spare sector is reassigned to substitute for a corresponding sector.


REFERENCES:
patent: 5150050 (1992-09-01), Genheimer et al.
patent: 5216655 (1993-06-01), Hearn et al.
patent: 5237553 (1993-08-01), Fukushima et al.
patent: 5610776 (1997-03-01), Oh
patent: 5774285 (1998-06-01), Kassab et al.
patent: 5954837 (1999-09-01), Kim

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