Mirroring Queue Prioritization for Cache Track Extents
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Solution Overview
Problem
Current data backup systems face inefficiencies in mirroring tracks from cache to secondary storage, leading to increased latency due to premature demotion of tracks from cache, which requires retrieval from primary storage, rather than direct mirroring from cache.
Innovation Solution
A method that processes extent information on modified tracks to prioritize mirroring queues, ensuring tracks with more modified data are mirrored from cache before being demoted, using a system that includes active and demote lists, and adjusts queue priorities based on the number of modified tracks and temporal bits, thereby optimizing the mirroring process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If tracks are demoted from cache before being transferred to secondary storage, then cache space is freed for further data, but the track must be retrieved from storage to transfer to secondary storage, increasing latency
Solution Approach 1:
The patent applies preliminary action by maintaining multiple mirroring queues that process extents before they are demoted from cache. Extents are staged in queues and processed for mirroring to secondary storage while still residing in cache, preventing the need to retrieve them from primary storage after demotion. This resolves the contradiction by enabling cache space freeing while avoiding the latency penalty of post-demotion retrieval.
2Device complexity
If all tracks are mirrored at the same rate, then the mirroring process is simple, but tracks with more modified data may be demoted before mirroring, reducing efficiency
Solution Approach 1:
The patent applies dynamics by implementing multiple mirroring queues with different processing rates based on extent characteristics. Extents are distributed across queues that process at varying speeds according to the number of modified tracks they contain, allowing dynamic adjustment of mirroring rates to match actual data characteristics. This resolves the contradiction by adapting mirroring complexity to data needs while maximizing mirroring efficiency for extents with more modified data.
3Productivity
If extent information is processed to prioritize mirroring queues, then tracks with more modified data are mirrored faster, but the system complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the mirroring process into multiple queues, each handling extents with specific characteristics (number of modified tracks). This segmentation allows the system to process extent information and assign priorities without requiring a single complex processing mechanism. Each queue operates independently with appropriate processing rates, resolving the contradiction by managing complexity through division while achieving high mirroring speed for modified tracks.
Data Source
AI summary
Provided are a computer program product, system, and method for indicating extents of tracks in mirroring queues based on information gathered on tracks in extents in cache. Extent information on an extent of tracks in a cache indicated in an active cache list is processed in response to destaging a track from the active cache list to add to a demote list used to determine tracks to remove from the cache. The extent information is related to a number of modified tracks in an extent destaged from the active cache list. The extent information for the extent is used to determine one of a plurality of mirroring queues to indicate the extent including modified tracks. A mirroring queue having a higher priority than another mirroring queue is processed at a higher rate to determine extents of tracks to mirror from the cache to the secondary storage.