Shingled magnetic recording disk drive with compensation for the effect of far track erasure (FTE) on adjacent data bands

Abstract

A shingled magnetic recording (SMR) disk drive has concentric shingled data tracks having data sectors with physical block addresses (PBAs), with the tracks being arranged in annular bands separated by annular inter-band gaps. The disk drive also has an on-disk extended cache region and may have writable inter-band cache (IBC) tracks in the inter-band gaps. A count is maintained in memory for each band and each IBC, and the count is incremented for each writing to a band or an IBC. When a count for a band or IBC reaches a predetermined threshold, the data is read from the tracks in the boundary region of the adjacent band that are within the range of the FTE and that data is then written to the extended cache. The FTE-affected tracks are then invalidated, meaning that PBAs can no longer be assigned to the data sectors in those tracks.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates generally to magnetic recording hard disk drives (HDDs), and more particularly to a shingled magnetic recording (SMR) HDD that compensates for the effect of far track erasure (FTE) on data tracks in the boundary regions of data bands.[0003]2. Description of the Related Art[0004]Magnetic recording disk drives that use “shingle writing”, also called “shingled recording” or “shingled magnetic recording” (SMR), have been proposed, for example as described in U.S. Pat. No. 6,185,063 B1 and U.S. Pat. No. 6,967,810 B2. In SMR, the write head, which is wider than the read head in the cross-track direction, writes magnetic transitions by making a plurality of consecutive circular paths that partially overlap. The non-overlapped portions of adjacent paths form the shingled data tracks, which are thus narrower than the width of the write head. The data is read back by the narrower read head. The narrower shi...

AI Technical Summary

Benefits of technology

[0009]The invention relates to a SMR HDD that essentially eliminates the effect of far track erasure (FTE) in the boundary regions of annular data bands caused by writing in the boundary regions of adjacent data bands, but without the need to continually read data from and rewrite data to bands affected by the FTE. The SMR disk has concentric shingled data tracks having data sectors with physical block addresses (PBAs), with the tracks being arranged in annular bands separated by annular inter-band gaps. The disk drive also has an extended cache region which is a plurality of concentric data tracks separated from the data bands, and at least some of the inter-band gaps may also have writable inter-band cache (IBC) tracks. A count is maintained in memory for each band and each IBC, and the count is incremented for each writing to a band or an IBC. When a count for a band or IBC reaches a predetermined threshold, such as a predetermined number within a predetermined time period, the data is read from the tracks in the boundary region of the adjacent band that are within the range of the FTE and that data is then written to the extended cache. The FTE-affected tracks are then invalidated, meaning that PBAs can no longer be assigned to the data sectors in those tracks.

Problems solved by technology

A problem in both conventional HDDs and SMR HDDs is wide-area track erasure (WATER) or far track encroachment or erasure (FTE).

Tracks on one side may encounter more pronounced FTE effects due to the write head shield design or due to read-write head skew.

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