Magnetic Disk Parity Sector Management for Rotational Delay Reduction
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Solution Overview
Problem
Magnetic disk devices face performance issues due to rotational delays when adding parity data to write data, and lack of valid parity data in sectors leads to unrecoverable read errors.
Innovation Solution
A magnetic disk device configuration that includes a controller to manage parity data by performing XOR operations on user data from other sectors, writing the generated parity data to specific areas without rotational delays, and updating parity sectors during read verify processing to ensure valid parity data is maintained.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If parity data is added to write data by On-The-Fly, then data reliability is improved, but performance is adversely affected
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing parity data in parity sectors before actual write operations occur. The controller pre-computes parity data for each track and stores it in designated parity sectors, so that when write operations are needed, the parity data is already ready and no additional processing time is required during the write operation itself.
2Productivity
If parity data is added to write data in the background, then performance is improved, but rotational delays occur before parity data is written
Solution Approach 1:
The controller pre-calculates parity data during idle periods or in the background and stores it in parity sectors before it is actually needed. This preliminary preparation eliminates the need for time-consuming operations during critical write paths, as the parity data is already computed and waiting in the appropriate sectors.
Solution Approach 2:
The patent creates a copy of the parity data in dedicated parity sectors that mirrors the structure and positioning of user data tracks. This copying approach allows the system to maintain separate parity information that can be quickly accessed and applied without interfering with the main data write operations, thereby reducing rotational delays.
3Device complexity
If valid parity data is not stored in the parity sector, then device complexity is reduced, but read-error recovery capability is lost
Solution Approach 1:
The patent segments the disk structure into distinct user data tracks and dedicated parity sectors, with each track having its own associated parity sector. This segmentation allows the system to maintain simple, organized parity data storage while ensuring that every data track has corresponding parity information available for error recovery, without requiring complex cross-track parity management.
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 solution enables efficient parity sector updating without rotational delays, enhancing data reliability and recovery capabilities by ensuring valid parity data is stored, thus improving overall performance and reliability of the magnetic disk device.
Implementation Method 1
a write head configured to write data to the disk
Implementation Method 2
a read head configured to read data from the disk
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a disk including a first recording area, a head includes a write head configured to write data to the disk, and a read head configured to read data from the disk, and a controller configured to set particular areas in same circumferential positions on tracks of the first recording area, and to write, to the respective particular areas, parity data based on data read from areas other than the particular areas.