Append-Only File System for Key-Value Stores
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Solution Overview
Problem
Existing file systems are not optimized for key-value stores, leading to inefficiencies such as high tail latency, write amplification, and increased storage costs due to unsuitable features and structures.
Innovation Solution
A specialized file system designed for key-value stores, featuring log-structured append-only write operations, separation of data and logs, pre-allocated data spaces, synchronous and asynchronous journal compaction modes, priority-based task scheduling, and support for zoned state drives (ZNS SSDs).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If general purpose file systems are used for key-value stores, then compatibility with existing systems is maintained, but tail latency increases and write amplification occurs
Solution Approach 1:
The file system segments data into separate data files and metadata files, with data files being append-only and metadata files being updated separately. This segmentation allows data writes to proceed without waiting for metadata updates, reducing tail latency while maintaining compatibility with existing key-value store interfaces.
Solution Approach 2:
The file system pre-allocates data spaces and pre-creates the necessary file structure before actual data writes occur. This preliminary setup eliminates the need for dynamic file creation and allocation during write operations, reducing write amplification and improving throughput.
2Device complexity
If general purpose file systems are used for key-value stores, then system simplicity is maintained, but write amplification increases
Solution Approach 1:
The invention extracts the data storage function from the metadata management function, creating separate data files that can be written to independently of metadata updates. This extraction eliminates the need to rewrite both data and metadata on every update, significantly reducing write amplification while keeping the overall system relatively simple.
Solution Approach 2:
The file system pre-allocates data spaces and pre-creates the necessary file structure before actual data writes occur. This preliminary setup eliminates the need for dynamic file creation and allocation during write operations, reducing write amplification and improving throughput.
3Device complexity
If data and logs are stored together in traditional file systems, then storage structure simplicity is maintained, but data loss in failures increases
Solution Approach 1:
The file system segments data into separate data files and metadata files, with data files being append-only and metadata files being updated separately. This segmentation allows data writes to proceed without waiting for metadata updates, reducing tail latency while maintaining compatibility with existing key-value store interfaces.
Solution Approach 2:
The file system implements a journaling mechanism that logs metadata changes before they are permanently written to disk. This journal acts as a cushion that allows recovery from failures by replaying logged operations, ensuring data integrity without requiring complex replication mechanisms.
4Reliability
If metadata is updated with every data write in traditional file systems, then data consistency is maintained, but metadata overhead increases
Solution Approach 1:
The file system segments data into separate data files and metadata files, with data files being append-only and metadata files being updated separately. This segmentation allows data writes to proceed without waiting for metadata updates, reducing tail latency while maintaining compatibility with existing key-value store interfaces.
Solution Approach 2:
The file system implements a journaling mechanism that logs metadata changes before they are permanently written to disk. This journal acts as a cushion that allows recovery from failures by replaying logged operations, ensuring data integrity without requiring complex replication mechanisms.
Data Source
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AI summary
A file system (100) particular for use with key-value stores is provided. The file system (100) can operate in a user space instead of a kernel space. The file system (100) can be an append-only file system. The file system (100) can support use of solid state drives, SSDs, for storage, including zoned SSDs. The file system (100) can include a file manager, a metadata manager, a task scheduler, a space allocator, and a collaborator for collaborating with a key-value store.