Metadata Management in Storage Control Devices
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Solution Overview
Problem
In storage systems, frequent modifications to user data cause rapid aging of high-speed memory caches due to the need to copy updated metadata from the first cache layer to the second cache layer, leading to reduced service life and increased costs.
Innovation Solution
A method and device for managing metadata by determining a first region for raw metadata in a cache page, updating metadata upon user data modification, and copying only the updated metadata to a shared high-speed memory, while merging metadata regions and redirecting access requests to optimize cache usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If updated metadata is copied to high-speed memory for every user data modification, then data access speed is improved, but high-speed memory service life deteriorates due to rapid aging
Solution Approach 1:
The patent applies partial action by copying only the modified metadata portions to high-speed memory rather than copying entire metadata structures. The system identifies specific modified cache pages and copies only those portions, reducing the frequency and volume of writes to high-speed memory while maintaining data access performance.
Solution Approach 2:
The patent implements discarding and recovering by allowing metadata to remain in the first cache layer longer and only promoting it to high-speed memory when necessary. The system recovers from frequent writes by using write buffering and batch operations, reducing the overall write frequency to high-speed memory.
2Reliability
If all metadata is copied to high-speed memory upon modification, then metadata consistency is improved, but system performance deteriorates due to increased write operations
Solution Approach 1:
The patent uses partial action by copying only modified metadata portions rather than all metadata. The system identifies specific changed cache pages and copies only those to high-speed memory, maintaining consistency where needed while reducing unnecessary write operations that would degrade performance.
Solution Approach 2:
The patent applies segmentation by dividing metadata into separate cache pages and tracking modifications at the page level. This allows the system to copy only the specific modified pages to high-speed memory rather than copying entire metadata structures, improving performance while maintaining consistency.
3Speed
If high-speed memory is used for metadata caching, then data access speed is improved, but system cost increases due to expensive hardware
Solution Approach 1:
The patent applies partial action by using high-speed memory only for storing modified metadata portions rather than allocating it for all metadata. This selective usage reduces the amount of expensive high-speed memory required while maintaining the performance benefits where they are most needed.
Solution Approach 2:
The patent uses parameter changes by dynamically adjusting the amount of high-speed memory allocated based on actual modification patterns. The system monitors metadata change frequencies and adapts the caching strategy, using high-speed memory intensively only when modification patterns justify the cost.
Data Source
AI summary
Techniques for managing metadata at a control device involve: determining, from a cache page corresponding to user data, a first region for storing raw metadata of the user data, the raw metadata including address information for storing the user data in a storage system; in response to the user data being modified, determining updated metadata of the modified user data to update the raw metadata in the first region; and copying the updated metadata to a high-speed memory shared by the control device and another control device. Accordingly, the techniques are capable of reducing the usage frequency of the high-speed memory, thereby extending the service life of the high-speed memory and reducing cost.