SSD Read Cache Management via Dual-Queue Segmentation
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Solution Overview
Problem
Conventional SSD cache management systems face issues with frequent data erase operations due to limited erase count, leading to reduced service life and increased maintenance costs, as they rely on conventional cache replacement algorithms that do not effectively manage data retention and write counts.
Innovation Solution
Implementing a read cache management method that inserts data blocks eliminated from the first queue into a second queue instead of deleting them directly, thereby increasing retention time and reducing write counts by writing metadata into the first queue, thus extending the service life of the SSD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional cache replacement algorithm (LRU) is used, then cache replacement is simple, but erase count increases and service life decreases
Solution Approach 1:
The patent segments the cache management into two distinct queues: a first queue for actively cached data blocks and a second queue for recently evicted data blocks. This segmentation allows differentiated management strategies - the first queue uses LRU for replacement decisions, while the second queue implements a time-based retention mechanism. By dividing the cache structure, the system reduces erase count without significantly increasing algorithmic complexity.
Solution Approach 2:
The patent implements preliminary action by pre-retaining evicted data blocks in the second queue before their actual deletion from the SSD. Instead of immediately deleting evicted blocks, the system holds them in the second queue for a predetermined time period, allowing potential recall if re-accessed. This preliminary retention action prevents premature deletions that would increase erase count.
2Productivity
If data blocks are constantly kicked out, then cache replacement frequency increases, but retention time decreases and erase count increases
Solution Approach 1:
The patent ensures continuity of useful action by maintaining data blocks in the second queue for a predetermined time period after eviction from the first queue. This continuous retention in the second queue extends the useful life of cached data blocks, allowing them to remain accessible for potential re-access while reducing the frequency of erase operations. The system continuously monitors and retains blocks rather than performing discrete, frequent delete operations.
3Productivity
If read hit ratio is increased, then performance improves, but more data blocks need to be retained increasing write operations
Solution Approach 1:
The patent extracts the retention function from the traditional single cache queue and creates a separate second queue dedicated to holding evicted but potentially reusable data blocks. This extraction allows the system to retain more data blocks (increasing potential read hit ratio) without proportionally increasing write operations to the SSD, as the second queue operates in memory rather than requiring SSD write operations for each retention.
Data Source
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AI summary
A read cache management method and apparatus based on a solid state drive, where the solid state drive includes a first queue and a second queue, and the method includes: receiving a read request, and determining whether the read request hits the first queue and the second queue (S101); if both the first queue and the second queue are missed, selecting and deleting an eliminated data block from the first queue according to a cache replacement algorithm (S102); if the eliminated data block is in a stored state, inserting the eliminated data block into the second queue (S103); and determining a target data block corresponding to the read request in a lower-level storage medium, and inserting the target data block into the first queue, where the target data block is in a non-stored state (S104). According to the foregoing read cache management method and apparatus based on the solid state drive, a hit ratio of the solid state drive can be increased, a data write count of the solid state drive can be reduced, and service life of the solid state drive can be extended.