SSD Cache Map Validation for Clustered Storage Node Recovery
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Solution Overview
Problem
Distributed storage systems with SSD caches face challenges in efficiently reconstructing data after node failure, leading to time-consuming and labor-intensive processes due to invalidation of entire SSD cache content.
Innovation Solution
A storage system with multiple nodes, each comprising an SSD cache and a management module, manages SSD cache maps to store mappings between logical and physical addresses, performs validation processes upon node rejoin, and invalidates entries based on current mappings and timestamps to ensure data integrity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire SSD cache content is invalidated upon node failure, then data integrity is ensured, but recovery time and effort increase significantly
Solution Approach 1:
The patent segments the SSD cache into individual data units with separate validity tracking. Instead of invalidating the entire cache, only specific data units are invalidated based on their individual validation status. This is achieved through maintaining an SSD cache map with separate entries for each data unit, allowing granular control over validity states.
Solution Approach 2:
The patent applies local quality by differentiating the validity state of individual data units within the SSD cache. Each data unit can have its own validity status independent of others, allowing the system to preserve valid data while invalidating only those units that may have become inconsistent due to node failure.
2Speed
If SSD cache is used to boost performance, then access time and latency are reduced, but data consistency across clustered nodes becomes more complex
Solution Approach 1:
The patent implements feedback mechanisms through validation processes that check data unit consistency when nodes rejoin the cluster. The system continuously monitors and validates cache data, using feedback from validation results to determine whether to invalidate or retain data units, thereby maintaining consistency without requiring complex manual intervention.
Solution Approach 2:
The system performs self-service through automated validation and invalidation processes. When a node fails and rejoins, the validation process automatically identifies and invalidates only the necessary data units without requiring manual intervention, reducing operational complexity while maintaining data consistency.
3Measurement precision
If validation process is performed upon node rejoin, then data accuracy is improved, but processing time during recovery increases
Solution Approach 1:
The patent applies partial action by performing validation only on specific data units that are relevant to the failed node's data range, rather than validating the entire SSD cache. This selective validation approach reduces processing time while maintaining data accuracy for the critical data units.
Data Source
AI summary
A storage system that includes multiple nodes, each node comprises a SSD cache and a management module and hard disk drives that are coupled to the nodes. The management module of each node is arranged to manage a SSD cache map that comprises multiple entries for storing mappings from logical addresses to SSD cache physical addresses and to physical addresses in the hard disk drives. The mappings are related to data units stored in the SSD cache. Upon a rejoin of a certain node following a shut-down or a failure of the certain node, the certain node is arranged to: obtain from at least one other node, current mappings between logical addresses and physical addresses in the hard disk drives, and perform a validation process of the data units stored in the SSD cache in response to relationships between the current mappings and the entries of the SSD cache map.