Magnetic Disk Drive Track Grouping for Refresh Control

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Solution Overview

Problem

Conventional magnetic disk drives face issues with side erase phenomena, leading to magnetic data degradation and read errors due to frequent side erase occurrences, which necessitate data refresh operations, but these operations can degrade drive performance and result in unwanted refreshing of tracks with low write counts.

Innovation Solution

A magnetic disk drive with a grouping module that partitions tracks into nonconsecutive groups, allowing for targeted data refresh based on write counts, using a refresh controller to manage the refresh process and prevent unnecessary refreshing by tracking write operations through a bitmap management system.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If data refresh is performed frequently to restore magnetically degraded data, then data reliability is improved, but drive performance deteriorates due to excessive refreshing operations

Engineering Contradiction:

Improvedata reliabilityVSAvoiddrive performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent changes the parameter of track grouping from consecutive to non-consecutive based on write count correlations. Tracks are grouped such that tracks with similar write count characteristics are placed together, allowing the refresh controller to identify and refresh only those tracks that actually need restoration, thereby reducing unnecessary refresh operations and improving drive performance while maintaining data reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent segments the set of tracks into multiple groups based on write count characteristics rather than treating all tracks uniformly. This segmentation allows differential refresh strategies to be applied to different track groups, refreshing only those tracks that have experienced significant magnetic degradation while leaving others untouched, thus resolving the contradiction between reliability and performance

Inventive Principle:

Principle #1Segmentation

2Device complexity

If conventional track grouping is used to reduce memory requirements, then device complexity is reduced, but unwanted refreshing occurs on tracks with low write counts

Engineering Contradiction:

Improvememory capacityVSAvoidrefresh accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies local quality by creating track groups with heterogeneous write count characteristics within each group. Specifically, each group contains a mix of tracks with different write counts, allowing the refresh controller to locally identify and refresh only the specific tracks that need it based on individual track write count thresholds, rather than refreshing entire groups uniformly. This prevents unwanted refreshing of tracks with low write counts while maintaining manageable memory requirements

Inventive Principle:

Principle #3Local quality

3Quantity of substance

If track pitch is reduced to increase recording density, then storage capacity is improved, but side erase phenomenon increases causing magnetic data degradation

Engineering Contradiction:

Improvestorage capacityVSAvoidside erase phenomenon

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent implements feedback by continuously monitoring write counts for each track and using this information to determine which tracks require refresh operations. The refresh controller reads the write count information and uses it to make intelligent decisions about which tracks to refresh, creating a closed-loop system that adapts to actual magnetic degradation patterns caused by side erase phenomena, thereby protecting data integrity in high-density storage environments

Inventive Principle:

Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach effectively reduces unwanted refreshing by accurately identifying tracks that require data refresh, thereby enhancing the performance and reliability of the magnetic disk drive by minimizing unnecessary operations.

Implementation Method 1

when data is magnetically written to a track, data (magnetic data) already magnetically written to the adjacent tracks may be magnetically degraded

Methodology Applied

Scientific EffectMagnetic field generation: Electromagnet

Implementation Method 2

the magnetic data in the adjacent tracks (more specifically, the intensity of a magnetic field from the magnetic data) may be weakened

Methodology Applied

Scientific EffectMagnetic field detection: Magnetic Field

Implementation Method 3

This rewrite of the magnetic data (that is, data refresh) allows a magnetic field from the magnetic data to be enhanced and stabled

Methodology Applied

Scientific EffectMagnetic field reinforcement: Magnetic Field

Data Source

PatentUS8345370B2Magnetic disk drive and refresh method for the same

Publication Date: 2013.01.01 KK TOSHIBA

AI summary

According to one embodiment, a magnetic disk drive includes a grouping module and a refresh controller. The grouping module partitions a set of tracks on a disk into a plurality of groups. Each of the plurality of groups includes a plurality of tracks including at least two tracks with nonconsecutive physical positions. The refresh controller controls refresh process for each of the plurality of groups.