Checkpointing Metadata in Content Addressable Storage
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Solution Overview
Problem
Conventional checkpointing arrangements in content addressable storage systems are inefficient when capturing and recovering metadata due to size limitations and availability restrictions in the metadata area, leading to difficulties in tracking and storing checkpointed metadata in the user data area.
Innovation Solution
The implementation of multi-level location arrays in the user data area to efficiently track and store checkpointed metadata, using page location arrays, array location arrays, and higher-level location arrays to map and store metadata locations, allowing for effective checkpoint capture and recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If checkpointed metadata is stored in the metadata area, then metadata is preserved, but size limitations and availability restrictions prevent efficient storage
Solution Approach 1:
The patent extracts checkpointed metadata from the metadata area and stores it in the user data area, which has greater available space. This resolves the contradiction by removing the storage burden from the constrained metadata area while preserving all checkpointed metadata in the more capacious user data area.
Solution Approach 2:
The patent introduces mapping information as an intermediary mechanism that bridges the metadata area and user data area. The mapping information contains location arrays that track where checkpointed metadata is stored in the user data area, enabling efficient retrieval without requiring the metadata area to directly hold all checkpointed metadata.
2Reliability
If conventional checkpointing arrangements are used, then system state can be recovered, but efficiency of checkpoint capture and recovery is poor
Solution Approach 1:
The patent performs preliminary actions by pre-allocating space in the user data area for checkpointed metadata and pre-establishing the mapping information structure with location arrays. This preliminary preparation enables efficient checkpoint capture and recovery operations without requiring complex real-time allocation or search operations.
Solution Approach 2:
The patent segments the storage of checkpointed metadata into organized units tracked by location arrays. The mapping information divides the user data area into manageable segments with explicit tracking, allowing efficient capture and recovery by working with segmented data structures rather than monolithic storage.
3Quantity of substance
If checkpointed metadata is stored in user data area, then storage capacity is sufficient, but tracking and retrieval becomes complex
Solution Approach 1:
The patent introduces mapping information as an intermediary layer between the user data area and the metadata management system. This mapping information contains location arrays that systematically track where checkpointed metadata is stored, simplifying retrieval operations without requiring complex search or tracking mechanisms.
Solution Approach 2:
The patent segments the tracking of checkpointed metadata into organized location arrays within the mapping information. This segmentation allows systematic tracking and retrieval by dividing the large user data area into manageable, trackable segments rather than requiring monolithic tracking of all stored metadata.
Data Source
AI summary
An apparatus in one embodiment comprises at least one processing device comprising a processor coupled to a memory. The processing device is configured to capture metadata from a metadata area of a storage system for checkpointing, and to store the captured metadata as checkpointed metadata in a user data area of the storage system in association with mapping information relating portions of the checkpointed metadata to particular storage locations in the user data area. The processing device in some embodiments is implemented within the storage system, and may comprise a storage controller of the storage system. The mapping information illustratively comprises a plurality of page location arrays each having a plurality of entries specifying respective locations of checkpointed metadata pages in the user data area. The mapping information may further comprise one or more array location arrays each indexed by a corresponding set of page location array identifiers specifying respective locations of page location arrays in the user data area.