Hard Disk Drive Repeatable Runout Error Compensation
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Solution Overview
Problem
Current hard disk drives (HDDs) face inefficiencies in storing and accessing non-synchronous repeatable runout (RRO) data, which takes up significant disk space and is time-consuming to process, due to its distribution across servo patterns and sectors.
Innovation Solution
Storing RRO data in a consolidated, compressed form within the reserved area of the disk, allowing it to be read into DRAM for decompression and predictive use, particularly utilizing shingled magnetic recording (SMR) for efficient write operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RRO data is stored in the servo pattern for each track or sector, then RRO correction can be applied accurately, but disk space is significantly reduced and manufacturing time increases
Solution Approach 1:
The patent extracts RRO data from the servo pattern and stores it separately in a dedicated RRO field in the disk reserved area. This separation allows the servo pattern to be minimized while RRO data is stored efficiently in a centralized location, resolving the contradiction between maintaining RRO correction accuracy and preserving disk space for user data.
Solution Approach 2:
The patent consolidates all RRO data for the entire disk into a single centralized field in the reserved area rather than distributing it across multiple servo patterns. This merging approach reduces the total servo overhead and increases areal density while maintaining the ability to apply accurate RRO corrections when the data is loaded into memory during operation.
2Measurement precision
If RRO data is stored in the servo pattern for each track or sector, then RRO correction can be applied accurately, but manufacturing time increases
Solution Approach 1:
The patent extracts RRO data measurement and storage from the per-track servo pattern writing process. Instead of measuring and writing RRO data for each individual track during manufacturing, the system measures RRO once and stores it centrally, significantly reducing manufacturing time while preserving RRO correction accuracy during operation.
Solution Approach 2:
The patent performs RRO measurement and data consolidation in advance during a single calibration phase, rather than during each track writing operation. This preliminary action reduces the overall manufacturing process time while ensuring accurate RRO correction data is available for all tracks.
3Area of stationary object
If RRO data is compressed and stored in the reserved area, then disk space is increased, but data access requires additional processing
Solution Approach 1:
The patent loads compressed RRO data from the reserved area into memory during drive initialization or idle periods before it is needed for operations. This preliminary loading action ensures that when RRO correction is needed during read/write operations, the data is already available in memory, minimizing access time penalties while maintaining the space savings from compression.
Data Source
AI summary
A method of correcting repeatable run out (RRO) errors for a HDD in which RRO data is instead stored in consolidated form within the reserved area of the disk, instead of storing RRO data in the servo patterns for each HDD track or sector. RRO data is preferably stored in the reserved area of a hard disk drive in compressed form. The compressed RRO data is subsequently read into DRAM in compressed form and then decompressed for use. Predictive techniques determine what compressed RRO data is needed for upcoming read/write operations.