Cache Stride Promotion for Latency Reduction
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Solution Overview
Problem
Current cache management systems in storage systems face inefficiencies in promoting tracks from a faster access cache to a slower access storage, leading to increased latency and resource wastage due to suboptimal handling of full and partial strides in the cache.
Innovation Solution
The system determines tracks to demote from the first cache and forms strides to write as full strides to the second cache, while demoting tracks from the second cache based on an LRU algorithm and consolidating valid tracks to maintain free strides, thereby improving cache promotion operations and resource utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tracks are promoted from first cache to second cache using traditional cache management techniques, then cache hit rate is improved, but I/O operation complexity increases and latency is reduced only partially
Solution Approach 1:
The patent segments the second cache into multiple strides, where each stride is a contiguous block of tracks. This segmentation allows the system to identify and promote complete strides as single units rather than individual tracks, reducing the number of I/O operations required and improving promotion efficiency while maintaining cache hit rate.
Solution Approach 2:
The patent merges multiple individual track promotions into a single stride promotion operation. By combining tracks that form complete strides and promoting them together in one I/O operation, the system reduces total operation time and latency while achieving the same cache hit rate improvement.
2Adaptability or versatility
If individual tracks are promoted from first cache to second cache, then cache flexibility is improved, but I/O operation efficiency deteriorates
Solution Approach 1:
The patent implements a dynamic stride promotion mechanism that adapts to the current state of the second cache. The system dynamically identifies which strides are complete and ready for promotion, and automatically adjusts promotion batches based on available space and stride completeness, maintaining cache flexibility while maximizing I/O efficiency.
Solution Approach 2:
The patent changes the fundamental parameter of promotion granularity from individual tracks to complete strides. This parameter change transforms the promotion process from numerous small operations to fewer larger operations, dramatically improving I/O efficiency while the system maintains adaptability through its ability to selectively promote based on stride completeness and cache space availability.
3Quantity of substance
If the second cache is filled with promoted tracks, then cache capacity utilization is improved, but available space for new tracks deteriorates
Solution Approach 1:
The patent performs preliminary actions by pre-identifying and marking complete strides in the first cache that are ready for promotion. This allows the system to batch promote multiple complete strides together before the second cache becomes full, maximizing capacity utilization while maintaining space for new tracks by proactively managing promotion queues.
Solution Approach 2:
The patent maintains continuous promotion operations by constantly monitoring both the first cache for complete strides and the second cache for available space. This continuous action ensures that promotion operations occur as soon as conditions are favorable, maximizing cache capacity utilization without allowing the second cache to become completely full and block new track admissions.
4Reliability
If partial strides are handled separately from full strides, then data integrity is improved, but operation complexity increases
Solution Approach 1:
The patent extracts and separates the handling of complete strides from partial strides. Complete strides are identified and promoted as atomic units to maintain data integrity, while partial strides are left in the first cache to be completed before promotion. This extraction simplifies the promotion logic by focusing on complete strides only, reducing operation complexity compared to handling mixed stride types together.
Data Source
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AI summary
Provided are a computer program product, system, and method for managing data in a cache system comprising a first cache, a second cache, and a storage system. A determination is made of tracks stored in the storage system to demote from the first cache. A first stride is formed including the determined tracks to demote. A determination is made of a second stride in the second cache in which to include the tracks in the first stride. The tracks from the first stride are added to the second stride in the second cache. A determination is made of tracks in strides in the second cache to demote from the second cache. The determined tracks to demote from the second cache are demoted.