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The ADvanced Systems Laboratory (ADSL)
Publication Abstract

Optimistic Crash Consistency

Vijay Chidambaram, Thanumalayan Sankaranarayana Pillai , Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau

Department of Computer Sciences, University of Wisconsin-Madison


We introduce optimistic crash consistency, a new approach to crash consistency in journaling file systems. Using an array of novel techniques, we demonstrate how to build an optimistic commit protocol that correctly recovers from crashes and delivers high performance. We implement this optimistic approach within a Linux ext4 variant which we call OptFS. We introduce two new file-system primitives, osync() and dsync(), that decouple ordering of writes from their durability. We show through experiments that OptFS improves performance for many workloads, sometimes by an order of magnitude; we confirm its correctness through a series of robustness tests, showing it recovers to a consistent state after crashes. Finally, we show that osync() and dsync() are useful in atomic file system and database update scenarios, both improving performance and meeting application-level consistency demands.

Full Paper: Postscript, PDF, BibTex
Talk Slides: PDF
Talk Video: Hosted by ACM   Hosted on Youtube
Source code: OptFS Software