Storage Control Device Retry Read Access Validation
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Solution Overview
Problem
Existing storage systems face reliability issues with read data accuracy when encountering 'recovered read error' responses, where data may be different from the originally written data due to positional shifts and adjacent track interference, leading to potential inaccuracies in read operations.
Innovation Solution
A storage system with a control unit that performs retry read accesses and uses cache memory to validate data integrity, comparing read data from retry operations with original data to ensure accuracy and perform diagnostics, and in redundant systems, transfers valid data from alternative disk devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If retry read access is performed for recovered read error responses, then data reliability is improved, but system complexity increases
Solution Approach 1:
The system performs preliminary comparison of retry read data with cached original data before finalizing the read operation. This preliminary action allows the system to detect potential data corruption early and determine whether retry is necessary, improving reliability while managing complexity through staged processing
Solution Approach 2:
The system implements feedback mechanisms where read data is compared between cache memory and retry operations, and error status is fed back to control retry behavior. This feedback loop ensures reliable data retrieval by continuously monitoring read success while maintaining controlled system complexity through automated decision-making
2Measurement precision
If retry read access is performed for recovered read error responses, then data accuracy is improved, but processing time increases
Solution Approach 1:
The system performs retry read access selectively rather than universally - only when recovered read error responses are detected. This partial action approach ensures data accuracy is improved for problematic reads while avoiding unnecessary retry operations that would waste processing time for already-correct reads
Solution Approach 2:
The system uses cache memory to store original data as a reference before retry operations, enabling preliminary comparison that can quickly verify data accuracy without full retry processing. This preliminary check reduces processing time by avoiding redundant retry operations when data is already correct
Data Source
AI summary
In a storage system, a disk device performs recovery and transfers read data to a control device, and the control device judges the validity of the recovery to prevent a transfer of erroneous data. A control device read-accesses a disk device, and the disk device returns read data and a recovered read error response. A control device, at the time of an initial recovered read error, performs a retry of a similar command, and if an error does not occur for read commands including the retry read command, judges the data to be valid. Uncertain data (suspect data) upon occurrence of a recovered read error is restored through disk retry, and accurate read data can be transferred to the host.