Electrical computers and digital processing systems: memory – Storage accessing and control – Control technique
Reexamination Certificate
1999-04-12
2001-08-21
Nguyen, Than (Department: 2187)
Electrical computers and digital processing systems: memory
Storage accessing and control
Control technique
C711S161000, C711S111000, C711S112000, C711S114000, C714S001000, C714S006130, C714S006130, C714S006130, C714S025000, C714S030000, C714S036000, C714S040000, C714S041000, C714S042000, C714S710000, C714S718000
Reexamination Certificate
active
06279089
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to hard disk drives. More particularly, the present invention relates to a method for managing defective data sites encountered during operation of the disk drive through a single defect management table.
2. Description of the Related Art
Hard disk drives store large volumes of data on one or more disks mounted on a spindle assembly. Disk drives employ a disk control system for interfacing with a host (e.g., a computer) to control the reading and writing of data on a disk. Each disk includes at least one disk surface which is capable of storing data. On each disk surface, user data is stored in data sectors (i.e., data sites) organized in concentric circular tracks between an outside diameter and an inside diameter of the disk.
As a result of the manufacturing process, defective data sites may exist on the disk surfaces of the disk drive. These defective data sites are conventionally termed “primary” defects. A defect discovery procedure is performed to locate these defects and mark them out as defective locations on the disk surface which are not available for use. A typical defect discovery procedure includes writing a known data pattern to the disk surface and subsequently reading the data pattern from the disk surface. Defective data sites are identified by comparing the data pattern read from the disk surface with the known data pattern written to the disk surface.
Following the defect discovery procedure, defective data sites are written to a primary defect list (PLIST). The primary defect list is used during formatting of the disk surface to generate a primary defect management table. Once identified in the primary defect management table, the defective data site may not be used for storing data and are passed over or “skipped” during disk drive operations.
Defective data sites encountered after formatting the disk surface are known as “grown defects” or “secondary defects”. Grown defects often occur in locations adjacent to defective data sites found during defect discovery. Grown defects are also written to a list, known as the grown defect list (GLIST), similar to that utilized for the primary defects. Grown defects encountered during the operation of the disk drive are added to a secondary defect management table. The secondary defect management table is utilized along with the primary defect management table during the operation of the disk drive for the identification of defective data sites on the disk surface. The defective data sites residing within the secondary defect management table are reassigned or “vectored” (i.e., mapped via an index pointer) to spare data site locations via a cross-reference entry (cylinder number, head number, and data sector number).
Thus, in prior art reassignment schemes, separate defect management tables are maintained for skipped data sites and reassigned data sites. The primary defect management table typically contains a list of data site addresses to be avoided during operation. In contrast, the secondary defect management table typically contains multiple cross-reference entries of data site reassignments, where each entry contains a defective data site address and a corresponding spare data site address which contains the reassigned data from the defective data site address. Due to limited bandwidth and operational memory, it is desirable to minimize the use and complexity of defect management tables which are active during read/write operations. The maintenance and use of two separate defect management tables during the operation of the disk drive results in operational inefficiencies.
There is a continuing need therefore for a defect management scheme which minimizes the operational inefficiencies while dealing effectively with defective data sites which are discovered during disk operations.
SUMMARY OF THE INVENTION
The present invention provides, in a disk drive driving having data sites on a disk, a method for accessing a series of logical data blocks which are mapped to sequential and non-sequential data sites to form a series of mapped data sites. The mapped data sites include a sequential string of data sites and a non-sequential data site, where the sequential string of data sites is terminated by a defective data site. The method begins by providing a defect table including entries for referencing defective data sites. The method next defines a skip type entry for the defect table, wherein the skip type entry includes a reference to a defective data site which is skipped. The method then defines a vector type entry for the defect table, where the vector type entry includes a reference to a defective data site which is reassigned to a secondary data site. Next, the method makes a skip type entry in the defect table to reference a skipped defective data site. The method then makes a vector type entry in the defect table to reference a skipped defective data site. Finally, the method accesses the series of mapped data sites using the defect table.
In one embodiment of the present invention, the method step of making a vector type entry in the defect table to indicate a reassigned defective data site includes two additional steps. In the first additional step, a vector cross reference entry for a reassignment cross-reference table associated with the defect table is defined. The vector cross-reference entry includes a reference to the defective data site which is reassigned and a corresponding reference to a reassignment data site. In the second additional step, a vector cross-reference entry is made in the reassignment cross-reference table to cross-reference the defective data site with the corresponding reassignment data site.
The defect table utilized by the present invention includes both primary defects and grown defects, which are represented by skip type entries and vector type entries, respectively. Both the skip type entries and vector type entries share a common field format. Each entry in the defect table comprises an entry type field and a location field. The location field of the defect table comprises an offset from an origin of a defect management partition.
The reassignment data site for a vector type entry is chosen from one or more spare data sites located on the disk. The one or more spare data sites are grouped into a pool of spare data sites, where a single pool of spare data sites exists on each disk. In one embodiment of the present invention, the pool of spare data sites contains approximately 1000 spare data sites. A spare pointer points to the next available spare data site within the pool of spare data sites. The spare pointer is incremented to point to the next available spare data site upon reassignment of the defective data site to a corresponding reassignment data site in the pool of spare data sites. In one embodiment of the present invention, the method is implemented in firmware residing within a disk control system of the disk drive.
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Schibilla Mark R.
Swatosh Timothy W.
Nguyen Than
Shara Milad G
Western Digital Technologies Inc.
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