We made our filesystem 47× faster by deleting it
4 days ago
- #filesystems
- #performance optimization
- #virtualization
- microsandbox v0.4 replaced a user-space filesystem with a Linux disk image, boosting speed 47× on average.
- File operations previously bounced through FUSE, causing slowdowns; now they stay inside the VM kernel.
- EROFS filesystem images are built in Rust, avoiding host tools and ensuring cross-platform compatibility.
- A single metadata image merges OCI layers, reducing VM devices needed and simplifying overlayfs.
- Benchmarks show dramatic improvements, like scanning Python standard library metadata from 500ms to 2ms.
- Host code shrunk by 5,300 lines, eliminating edge cases by leveraging kernel overlayfs instead of reimplementing.
- Writes remain copy-on-write, and first pulls aren't faster, but subsequent sandbox creation is quicker.
- Lesson: kernel primitives often outperform user-space designs; custom tools were needed to keep promises.