Exporting Transactional Interface to Applications in Log-Structured File Systems

The write-ahead-logging (WAL) used in SQLite adopts roll-forward mechanism to ensure system consistency, which induces double writes of the updates due to the checkpointing procedure. F2FS is a recent proposed file system that is specifically designed and optimized for flash memory based storage. By leveraging the log-structured update pattern and the atomicity of filesystem-level checkpoint in F2FS, this paper proposes an index remapping mechanism to redirect the DB access to WAL. In this way, the write amplification caused by WAL checkpointing can be mitigated, which further improves the overall performance of the system. The atomicity of the remap operation and the WAL alignment format are discussed in details. In addition, crash recovery under the proposed framework is validated. The experimental results show that the proposed framework can effectively reduce the write traffic and improve system performance.