SSD File Writing by Failure-Time Grouping to Cut Write Amplification
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Solution Overview
Problem
Fragmentation of data storage in SSDs leads to increased write amplification and inefficient memory usage due to the mixing of files with different degrees of hotness and coldness, resulting in higher write overhead.
Innovation Solution
The method involves allocating reclaim unit handles based on file failure times to minimize differences between the failure times of files within the same reclaim unit, ensuring synchronous erasure during garbage collection and reducing fragmentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If files with different access frequencies are stored in the same reclaim unit, then storage space utilization is improved, but write amplification increases due to premature garbage collection
Solution Approach 1:
The patent segments the storage space by dividing it into multiple reclaim units (RUs) organized in reclaim groups (RGs). Each RU is further divided into data regions and metadata regions. This segmentation allows files with different access frequencies to be distributed across different RUs, preventing premature garbage collection while maintaining storage space utilization.
Solution Approach 2:
The patent applies local quality by assigning different characteristics to different regions within the storage structure. Specifically, the metadata region contains file mapping information that allows the system to identify valid vs. invalid data locally within each RU, enabling precise garbage collection decisions that reduce write amplification while maintaining efficient space utilization.
2Quantity of substance
If files with different failure times are mixed in the same reclaim unit, then storage capacity is maximized, but garbage collection efficiency deteriorates due to synchronous erasure requirements
Solution Approach 1:
The patent implements preliminary action by pre-calculating and storing failure time information for each file in the metadata region of the reclaim unit. This allows the garbage collection process to efficiently identify files that can be erased together without requiring complex runtime analysis, thereby maintaining both storage capacity and garbage collection efficiency.
3Loss of substance
If valid data is moved to a new reclaim unit during garbage collection, then space reclamation is achieved, but write overhead increases
Solution Approach 1:
The patent extracts the metadata region from the reclaim unit structure, allowing it to be processed and updated independently from the data region. This extraction enables the system to update file mapping information and erase invalid data without necessarily moving valid data to new RUs, thereby achieving space reclamation with reduced write overhead.
Data Source
AI summary
A method of writing a file, including acquiring a plurality of target files to be written; determining, for each of the plurality of target files, a feature value associated with a file failure time of each of the plurality of target files; allocating a reclaim circuit handler to each target file based on the feature value of each target file such that differences between failure times of individual files contained in a reclaim circuit pointed to by the reclaim circuit handler are less than a preset threshold value, each reclaim circuit handler being one of a preset plurality of reclaim circuit handlers; writing each target file into the reclaim circuit pointed to by the reclaim circuit handler allocated to each target file.