Western Digital Technologies, Inc.

Western Digital Corporation

Lsi Corporation

Mark R Schibilla

Timothy W Swatosh

Randy Reiter

Greg Kittilson

Described embodiments provide a method of recovering storage space on a solid state disk (SSD). An index and valid page count are determined for each block of a segment of an SSD. If the valid page count of at least one block in the segment is zero, a quick clean is performed. A quick clean deallocates blocks having zero valid pages and places them in a queue for erasure. Otherwise, a deep clean is performed. A deep clean determines a compaction ratio, N-M, wherein N is a number of partially valid blocks and M is a number of free blocks required to compact the valid data from the N partially valid blocks into M entirely valid blocks. At least one data structure of the SSD is modified to refer to the M entirely valid blocks, and the N partially valid blocks are placed in the queue for erasure.

Garbage collection for solid state disks

A method for recovering data from marginally defective data sites on a disk drive surface. If a user data site is determined to be marginally defective during a read operation, a read error recovery procedure is performed on the marginally defective data site. The read error recovery procedure begins by conditionally reassigning data from the marginally defective data site to a spare data site. Next, the data from the marginally defective data site is rewritten to the marginally defective data site. If the data rewrite operation is successful, the method ends. If the data rewrite operation fails, the conditionally reassigned data from the marginally defective data site is reassigned to the spare data site.

Rewrite with embedded reassign for data recovery from marginally defective data sites on a data storage device

A method of managing defective data sites on a hard disk drive through a shared defect table. The method writes both skip type entries and vector type entries to the defect table. Skip type entries represent defective data sites that are to be skipped during operation of the disk drive, and vector type entries represent defective data sites which have been reassigned to spare data sites and alternate locations on the disk. Both skip type entries and vector type entries are in a common format within the defect table, where the top two data bits of each entry distinguish skip type entries from vector type entries. The method also manages a separate cross-reference table for vector type entries, where the location of the reassigned defective data site is associated with the location of a spare data site which contains the data from the reassigned site. The shared defect table provides an efficient way for distinguishing skipped and vectored defective data sites during subsequent disk operation.

Defective data site management through a shared defect management table

A method for reassigning a defective data site on a disk surface of a disk drive during a write operation. When a write error is detected while writing a data block to a user data site, a write error recovery procedure is performed on the user data site. If the write error recovery procedure determines that the user data site contains an unrecoverable error, the data block is written to a spare data site located at a different area of the disk surface, and a cross-reference entry for the reassignment is stored in memory on the disk drive. Upon completion of the write operation, the user data sites encountering write errors are reassigned to the spare data sites. The reassignment operation includes marking all user data sites encountering write errors as defective data sites, adding all user data sites encountering write errors to a list of defective data sites, and writing the reassignment cross reference entries stored in the disk drive memory to the disk surface. The method can handle reallocation of multiple unrecoverable data sites within each disk write operation.

On the fly write reallocation

A disk drive employs a method for writing a block of data (or multiple blocks of data) to a data region following a defective servo sectors. The disk drive includes a sampled head positioning servo system and a rotating disk with a plurality of data tracks on a surface of the disk. Each data track has multiple spaced-apart sequentially-active servo sectors. Data regions are disposed between the servo sectors. The method includes the step of executing a command to perform a write operation to write a data block to a target data region. A defective servo sector S.sub.n is encountered preceding the target data region during the write operation. The defective servo sector S.sub.n precedes a servo sector S.sub.n+1 and follows a servo sector S.sub.n-1. A timer interval is set to enable a first detection window Dw.sub.n+1 for detecting a field in servo sector S.sub.n+1 . If the field is detected within the detection window Dw.sub.n+1, a field is detected within a detection window Dw.sub.n-1 for the servo sector S.sub.n-1. The data block is written in the target data region following the defective servo sector S.sub.n based on detecting the field within the detection window Dw.sub.n-1 for the servo sector S.sub.n-1 . A timer interval is set to enable a second detection window Dw.sub.n+1 for detecting a field in the servo sector S.sub.n+1 . If the field in the servo sector S.sub.n+1 is detected within the second detection window Dw.sub.n+1, the data block is marked as being successfully written.

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Rochester, MN, United States of America

Mark R Schibilla