Magnetic Head Seek Latency via Media Bump Detection

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Solution Overview

Problem

In magnetic disk drives, the dynamic flying height (DFH) control and media bump avoidance lead to rotational latency due to unconsidered seek latency, degrading performance by delaying seek operations.

Innovation Solution

A magnetic disk drive system that includes a determiner to assess the presence of media bumps influencing DFH control, a calculator to quantify the necessary latency for bump avoidance, and a selector to optimize command reordering by incorporating this latency, thereby reducing rotational latency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If media bump avoidance control is executed together with DFH control, then the magnetic heads can avoid colliding with media bumps, but seek latency increases and rotational latency occurs

Engineering Contradiction:

Improvemedia bump avoidanceVSAvoidrotational latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system preliminarily determines the presence of media bumps in the seek path and calculates the additional latency required for avoidance before command selection. This allows the reordering operation to anticipate and account for the latency impact, selecting commands that can be executed without suffering from rotational latency caused by seek delays.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system incorporates feedback from media bump information into the command reordering process. By using the calculated latency as feedback, the reordering operation can adjust command selection to avoid rotational latency, creating a closed-loop system that continuously optimizes seek performance based on actual media conditions.

Inventive Principle:

Principle #23Feedback

2Reliability

If seek operations are delayed for media bump avoidance, then head collision is prevented, but seek time increases and performance degrades

Engineering Contradiction:

Improvehead collision avoidanceVSAvoidseek performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system performs preliminary determination of media bump presence and calculates the latency impact before the actual seek operation. This advance knowledge allows the reordering operation to select commands that minimize performance degradation, effectively preparing the system in advance to handle the seek delay optimally.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts command reordering based on real-time media bump information and calculated latency. Rather than using fixed seek time estimates, the system adapts command selection to the actual conditions, dynamically optimizing performance while maintaining safety margins for head collision avoidance.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS10431247B2Magnetic head control capable of avoidance media bumps during seeking process

Publication Date: 2019.10.01 KK TOSHIBA

AI summary

According to one embodiment, a magnetic disk drive selects in command evaluation in reordering processing, a command accessible in a shortest time. The device determines whether media bumps which influence a dynamic flying height (DFH) control exist in a seek section between completion of a previous command and start of a selected command or not, calculates a latency necessary for avoidance of the media bumps if it is determined by the determination that the media bumps which influence the DFH control exist, and selects the command accessible in the shortest time including the time obtained by summing the latency calculated by the calculation as the command to be next processed.