Flash Array Controller Stripe-Level Garbage Collection
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Solution Overview
Problem
Flash arrays face high write amplification during system garbage collection, leading to reduced solid state disk lifespan and insufficient allocable logical addresses, as existing methods lack precision in identifying and managing areas with dense invalid data.
Innovation Solution
A system controller that performs garbage collection at a finer granularity of stripes, selectively targeting stripes with maximum invalid data volumes, and strategically managing logical addresses to reduce write amplification and extend disk lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If system garbage collection is performed on logical chunk group basis, then allocable logical addresses are released, but write amplification increases and solid state disk lifespan decreases
Solution Approach 1:
The patent segments the logical chunk group into multiple stripes as independent garbage collection units. Instead of collecting entire logical chunk groups, the system identifies and collects only those stripes containing invalid data, reducing the scope of data migration and write amplification while maintaining effective address space management.
Solution Approach 2:
The patent applies local quality by treating different stripes within a logical chunk group differently based on their invalid data characteristics. Stripes with high invalid data ratios are selected for collection, while stripes with low invalid data ratios are preserved, optimizing the balance between address release and write amplification reduction.
2Area of stationary object
If system garbage collection moves all valid data in a logical chunk group, then space is released, but the quantity of write amplification times increases
Solution Approach 1:
The patent extracts only the necessary stripes containing invalid data from the logical chunk group for garbage collection, rather than moving all valid data in the entire logical chunk group. This selective extraction reduces the volume of data migration and associated write amplification while still releasing sufficient space.
Solution Approach 2:
The patent applies partial action by performing garbage collection on only a portion of the logical chunk group (specific stripes with invalid data) rather than the entire logical chunk group. This partial collection achieves space release with minimal write amplification by avoiding unnecessary data movements.
3Productivity
If existing methods lack precision in identifying areas with dense invalid data, then garbage collection efficiency decreases, but write amplification increases
Solution Approach 1:
The patent replaces coarse-grained logical chunk group-level garbage collection with fine-grained stripe-level garbage collection. This substitution enables precise identification of stripes with dense invalid data through metadata tracking, improving garbage collection efficiency while minimizing unnecessary data movements and write amplification.
Data Source
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AI summary
A flash array provided in embodiments includes a controller and a solid state disk group, the solid state disk group includes a plurality of solid state disks, the plurality of solid state disks include a logical chunk group, and the logical chunk group includes a plurality of stripes. The controller is configured to: count a data volume of invalid data included in each of the plurality of stripes, and select at least one target stripe from the plurality of stripes, where the target stripe is a stripe that includes a maximum volume of invalid data among the plurality of stripes. Then, the controller instructs the solid state disk group to move valid data in the target stripe, and instructs the solid state disk group to delete a correspondence between a logical address of the target stripe and an actual address of the target stripe. This can reduce write amplification, thereby prolonging a life span of the solid state disk.