Flash Storage Garbage Collection via Data Stability Bins
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Solution Overview
Problem
Flash storage devices face inefficiencies in data management due to the need for block-level erasure, leading to unnecessary data staleness and storage space wastage during garbage collection, as existing methods do not effectively identify the most stable data blocks for removal.
Innovation Solution
A storage device algorithm that arranges data blocks into bins based on valid and invalid data ratios, selects data blocks with lower change rates as 'garbage' blocks, and copies valid data from these blocks to other blocks, thereby minimizing new stale data creation and optimizing storage space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If data blocks are selected for garbage collection based solely on valid data ratio, then garbage collection can be performed on full blocks, but stable data blocks may be incorrectly selected as garbage blocks causing unnecessary data migration and storage space wastage
Solution Approach 1:
The patent changes the selection parameter from static valid data ratio to dynamic rate of change of valid data to invalid data. By monitoring how quickly valid data becomes invalid in each block, the system can identify stable blocks (low rate of change) versus unstable blocks (high rate of change), preventing selection of stable blocks for garbage collection and reducing unnecessary data migration and storage wastage
Solution Approach 2:
The system implements feedback by continuously monitoring the rate of change of valid data to invalid data in each block. This feedback mechanism allows the system to adaptively identify which blocks are most suitable for garbage collection based on actual data stability patterns, rather than using a fixed threshold, thereby improving garbage collection efficiency while minimizing storage space wastage
2Reliability
If block-level erasure is performed in flash memory, then data can be erased completely, but entire blocks must be erased even when only some data needs updating
Solution Approach 1:
The patent extracts only the necessary valid data from selected blocks before performing block-level erasure. By identifying and migrating only the stable valid data that needs to be preserved, the system minimizes the amount of data that must be relocated and reduces storage space wastage, while still achieving complete erasure of the selected blocks when needed
Data Source
AI summary
A storage device implements a method for garbage collection. The storage device arranges data blocks of a storage medium into a bin and determines first coldness of a first data block in the bin and second coldness of a second data block in the bin that are respectively associated with a first rate of change of valid data in the first data block into invalid data and a second rate of change of valid data in the second data block into invalid data. Based on the first coldness and the second coldness, the storage device selects a colder data block from the first and second data blocks as a garbage data block. Because the valid data in the selected garbage data block are more stable, they may cause less new stale data or garbage data in a new block to which the valid data are moved.