SSD Garbage Collection via Dual-Table Reverse Mapping
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Solution Overview
Problem
Current distributed storage systems face challenges in efficiently performing garbage collection, leading to storage location exhaustion and impaired system performance due to limitations in address space and overhead associated with garbage collection processes, especially in systems using Solid-State Disks (SSDs) where traditional HDD-based mapping table allocation algorithms are inadequate.
Innovation Solution
A system and method that utilize two tables - one mapping virtual addresses to storage locations and another for reverse mappings - with a data storage controller configured to identify segments for garbage collection, copy data to new locations, and reclaim storage space, while also deduplicating data and correcting errors during relocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional HDD-based mapping table allocation algorithms are used in SSD systems, then ease of operation is maintained, but storage capacity and address space support are insufficient
Solution Approach 1:
The patent changes the fundamental parameters of mapping table management by transitioning from HDD-based allocation algorithms to SSD-based algorithms that utilize wear-leveling and dynamic address space management. This enables the system to support larger address spaces while adapting to SSD-specific characteristics such as limited write endurance and different performance characteristics.
Solution Approach 2:
The system implements dynamic mapping table allocation and garbage collection mechanisms that adapt to changing storage conditions in real-time. The controller dynamically adjusts mapping tables based on wear patterns, available capacity, and performance requirements, enabling flexible address space management that grows with data needs while maintaining optimal SSD operation.
2Productivity
If garbage collection is performed frequently to reclaim storage space, then storage location availability is improved, but system performance is impaired due to overhead
Solution Approach 1:
The system performs preliminary actions by proactively managing wear patterns and pre-allocating storage blocks before they become problematic. The controller monitors storage conditions and initiates garbage collection operations in advance, during low-activity periods, to prevent performance degradation before it occurs rather than reacting to problems after they manifest.
Solution Approach 2:
The patent implements periodic garbage collection cycles that are strategically scheduled to balance space reclamation with performance maintenance. Rather than continuous garbage collection, the system uses periodic batches timed to coincide with low I/O activity periods, thereby reclaiming storage space while minimizing impact on overall system performance.
3Quantity of substance
If mapping tables are expanded to support larger address spaces, then storage capacity is improved, but device complexity increases
Solution Approach 1:
The patent segments the mapping table structure into multiple manageable components including translation lookup tables (TLBs), garbage collection tables, and wear-leveling tables. This segmentation allows the system to handle large address spaces by dividing the complex mapping function into smaller, specialized tables that can be independently managed and optimized for specific purposes.
Solution Approach 2:
The controller acts as an intermediary layer between the logical address space and physical storage locations, managing the complexity of mapping through intelligent algorithms. The controller mediates between the need for large address space support and the limitations of SSD architecture by implementing virtualization techniques and dynamic mapping strategies that abstract the complexity from the storage interface.
Data Source
AI summary
A system and method for performing garbage collection. A system includes a storage medium, a first table including entries which map a virtual address to locations in the storage medium, and a second table with entries which include a reverse mapping of a physical address in a data storage medium to one or more virtual addresses. A storage controller is configured to perform garbage collection. During garbage collection, the controller is configured to identify one or more entries in the second table which correspond to a segment to be garbage collected. In response to determining the first table includes a valid mapping for a virtual address included in an entry of the one of the one or more entries, the controller is configured to copy data from a first location identified in the entry to a second location in the data storage medium, and reclaim the first storage location.