Garbage Collection Bitmask for Data Storage Metadata
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Solution Overview
Problem
Data storage devices face inefficiencies due to the extensive effort required to maintain accurate metadata, which burdens system resources and leads to inefficient use of memory, especially when managing multiple versions of data and identifying stale data for garbage collection.
Innovation Solution
Implementing a system with garbage collection units (GCUs) that utilize a bitmask and sequence map stored in a header region to monitor and update metadata in real-time, allowing for the identification of stale data without accessing metadata, and maintaining a bitmask table and hierarchical log in separate caches for efficient data management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If metadata is extensively mapped to track all data versions and locations, then data retrieval accuracy is improved, but system resource burden and operation time increase significantly
Solution Approach 1:
The patent segments the memory space into garbage collection units (GCUs), each with its own header region containing a bitmask. This segmentation allows the system to track data validity at the GCU level rather than maintaining comprehensive metadata for every data version, reducing overall metadata complexity while preserving retrieval accuracy through localized tracking.
Solution Approach 2:
The patent introduces a bitmask as an intermediary data structure that indirectly tracks data validity without requiring direct metadata mappings for all data versions. The bitmask serves as a compact mediator between the physical memory locations and the logical data validity state, reducing the burden of extensive metadata management.
2Measurement precision
If comprehensive metadata mapping is maintained to identify stale data, then garbage collection accuracy is improved, but operation speed and productivity decrease
Solution Approach 1:
The patent performs preliminary actions by setting and updating bitmask values at the time of data writing and invalidation. Instead of requiring comprehensive metadata mapping during garbage collection, the system has already prepared the validity state information in the bitmask, enabling rapid identification of stale data without extensive processing during the garbage collection operation.
3Measurement precision
If real-time metadata updates are performed for every data version, then data version tracking accuracy is improved, but system resource consumption and time overhead increase
Solution Approach 1:
The patent extracts the essential validity tracking information into a compact bitmask structure stored in the GCU header, separating this critical information from the full metadata that would otherwise need to be maintained. This extraction allows the system to track data version validity with minimal overhead, storing only the necessary validity state rather than complete metadata for each version.
Data Source
AI summary
Method and apparatus for handling data in a data storage device. In accordance with some embodiments, a memory space with a plurality of garbage collection units (GCUs) that are each arranged into pages of memory that store user data identified by logical addresses (LAs) and each GCU has a metadata region that stores metadata that correlates the LAs with physical addresses (PAs). A header region in each page of memory stores a bitmask and a sequence map of the LAs in each page that are used by a log manager to creates a bitmask table stored in a first cache and a hierarchical log stored in a second cache. The bitmask table and hierarchical log are used to determine when the LAs stored in the selected GCU are stale, and update the bitmask for each page in the selected GCU after the stale data has been erased.