Direct Read Control via Generation Identifier Verification
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Solution Overview
Problem
In computer storage systems with multiple controllers, hosts face challenges in directly reading data from a shared physical storage space without risking invalid data access, as metadata can become outdated due to concurrent write operations, leading to potential reading of incorrect data.
Innovation Solution
Implementing a generation identifier stored within each physical data block during write operations, allowing hosts to verify data validity by matching the current identifier with an expected one, and requesting updated metadata if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hosts directly read data from shared physical storage space, then system performance is improved, but data validity cannot be guaranteed due to outdated metadata
Solution Approach 1:
The system performs preliminary actions by storing the generation identifier in the metadata cache along with the physical address information before the host reads data. This allows the host to verify data validity in advance by comparing the generation identifier in the cached metadata with the current generation identifier stored in the physical data block, thus preventing reading of outdated data while maintaining direct read performance
Solution Approach 2:
The system implements a feedback mechanism where the host reads the generation identifier from cached metadata, compares it with the current generation identifier from the physical data block, and determines whether to read the data or request updated metadata. This feedback loop ensures data validity is verified while allowing direct read operations to proceed when data is current, thus resolving the contradiction between performance and reliability
2Reliability
If metadata is updated frequently to ensure data validity, then data accuracy is improved, but system performance deteriorates due to additional verification overhead
Solution Approach 1:
The system changes the parameter representation by using a generation identifier (a compact numerical value) instead of maintaining complex metadata update protocols. This allows efficient verification of data validity through simple numerical comparison, improving both data accuracy and performance by reducing the overhead of metadata management
Data Source
AI summary
The presently disclosed subject matter includes various inventive aspects, which are directed to direct read access of a host computer device to a share storage space in a data storage system, as well as control of the direct read of the host computer device by a control computer device in the data storage system.