Error detection/correction and fault detection/recovery – Data processing system error or fault handling – Reliability and availability
Reexamination Certificate
2001-01-04
2004-04-20
Beausoliel, Robert (Department: 2184)
Error detection/correction and fault detection/recovery
Data processing system error or fault handling
Reliability and availability
C714S710000, C711S170000, C369S053150, C369S053170
Reexamination Certificate
active
06725395
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates in general to a disk drive apparatus such as a hard disk drive, and in particular, to a technique for fast writing or reading data into or from an alternative sector if a data track of a recording medium contains a defective sector and more particularly, to a technique suitable for handling audio-visual data.
2. Description of the Related Art
A hard disk drive is one of the most popular external storage devices for a computer. As is well known, the surface of a hard disk (also called a “magnetic disk”), which is the recording medium in the hard disk drive, is divided into circular tracks and each track is radially divided into sectors, which are the smallest storage units on the disk. The tracks near the edge of the hard disk provide a higher line storage density than tracks nearer the center. With the “Zone-Bit Recording” scheme, which is a today's dominating data recording technique for hard disks, all the tracks are grouped into zones so that each zone has a constant line storage density. The length of each sector is typically 512 bytes, so tracks nearer the edge of the hard disk contain more sectors.
Tracks are not necessarily in good condition. A track may contain a defective sector in which data cannot be written or read due to a flaw or dust. If a defective sector is detected in the manufacturing process of a hard disk, an alternative sector is allotted in place of the defective sector. A defective sector may not always occur in the manufacturing process. It may occur in use after delivery. Also in such a case, an alternative sector is allotted in place of the defective sector. The allotment of an alternative sector in a manufacturing process is called “assignment” and the allotment of an alternative sector after delivery is called “re-assignment.”
A group of sectors to be used as alternative sectors are positioned in a specific area on a hard disk. For example, in a case of the above-described zone-bit recording the alternative sector area may be provided in a specific area in an outer track and an inner track of each zone in the radial direction of the disk. Therefore an alternative sector and an original replaced sector are typically not in the same track. When data stored in the alternative sector is read, the magnetic head actuator of the hard disk drive should perform a seek operation from a track containing the original sector to the inner or outer track in the same zone. Because the seek operation is performed each time data is read from the re-assigned alternative sector, the performance of the hard disk drive momentarily decreases when alternative sectors are successively accessed to read data.
The re-assignment is performed to an alternative sector in the nearest sector area to the defective sector. Therefore, if a major defect occurs in the radially middle of the zone (hereinafter called simply the “middle of a zone”) and a number of sectors become defective, the re-assignment may be performed to alternative sectors in both of the inner and outer alternative sector area. This requires seek operations between the inner alternative sector and the outer alternative sector, thereby aggravating the momentary performance decrease. Especially when audio/visual data is handled, the momentary performance decrease may lead to a momentary halt of a moving image or a sound skip and therefore should be taken seriously compared to cases where computer data is handled.
Various solutions to the performance decrease due to seek operation have been proposed.
For example, Published Unexamined Patent Application No. 5-66999 proposes a method for storing and managing data recorded in an alternative sector on a hard disk in cache memory of the hard disk apparatus. In the hard disk apparatus, data in the alternative sector is stored and managed in the cache memory, which is fast memory, and when the data is to be read, the data in the cache memory is accessed and read instead of accessing the hard disk which takes much time for an access. Thus the data can be read quickly.
Published Unexamined Patent Application No. 11-232046 discloses a method for reading, in addition to data stored in an alternative sector to be read, data stored in an alternative sector subsequent to an alternative sector and storing the data in memory for alternative sector. With this method, instead of accessing a plurality of alternative sectors separately, data stored in the plurality of sectors are accessed and read at a time, thereby reducing the number of accesses. In addition, because a hard disk takes time of milliseconds for an access whereas the memory allows for access time of nanoseconds, time required for reading data from alternative sectors can be significantly reduced.
For magneto-optical disks, Published Unexamined Patent Application No. 8-167250 discloses an apparatus which allows a defect remedy process to be performed quickly by providing in a disk drive a buffer storage section formed of semiconductor memory as a backup storage for temporarily storing data, besides conventional alternative sectors.
The above-mentioned approaches described in Published Unexamined Patent Applications Nos. 5-66999, 11-232046, and 8-167250 are effective for the reduction of time required for reading data from alternative sectors.
The technology disclosed in Published Unexamined Patent Application No. 5-66999 previously stores all data stored in all alternative sectors of a hard disk in cache memory. Today, this method for storing data stored in all alternative sectors in cache memory is impractical because the storage capacity of recent hard disk devices is enormous.
Published Unexamined Patent Application No. 11-232046 provides the description of reading data in alternative sectors the number of which optimized by the memory device. It, however, does not propose a specific method for optimizing the number of alternative sectors for reading data from the alternative sectors.
The technology disclosed in Published Unexamined Patent Application No. 8-167250 involves the provision of a buffer storage section. However, providing such a new component increases the cost of the product.
Therefore, it is an object of the present invention to provide a method for reading data in alternative sectors faster without providing additional memory for storing data stored in alternative sectors, that is, without adding a new hardware component to a hard disk drive, unlike Published Unexamined Patent Application No. 8-167250.
SUMMARY OF THE INVENTION
If a number of defective sectors occur in the middle of a zone and they are within a given distance from one another, data to be written in these sectors are likely to be a series of related items of data and it would be effective to write the data in alternative sectors in one of the inner and outer alternative sector areas in the zone regardless of the distance between each defective sector and the outer or inner alternative sector area. With conventional methods in which defective sectors are re-assigned to inner or outer alternative sectors depending on the distance between a defective sector and the inner or outer area in a zone, a series of related items of data is re-assigned both of the inner and outer alternative sectors in the zone, therefore a seek operation is required between the inner and outer areas of the zone in order to read the data. On the contrary, with the method described earlier in which defective sectors are re-assigned to alternative sectors in one of the inner and outer alternative sector areas if they are within a given distance from one another, the seek operation across the zone is not required in order to read a series of related items of data from the alternative sectors. This means that data can be read faster from the alternative sectors.
While the method has been described with respect to an example in which a number of defective sectors are re-assigned to alternative sectors in one of the inner and outer areas if they are within a given distance from one another, in
Asano Hideo
Kanamaru Atsushi
Ono Hiroyuki
Beausoliel Robert
Bracewell & Patterson L.L.P.
Hitachi Global Storage Technologies - Netherlands B.V.
Manoskey Joseph D
Raissinia Abdy
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