Performance optimization of the VDFS verified file system

Abstract

Formal verification of software has become a powerful tool for creating software systems and proving their correctness. While such systems provide strong guarantees about their behavior, they frequently exhibit poor performance relative to their unverified counterparts. Verified file systems are not excepted, and their poor performance limits their utility. These limitations, however, are not intrinsic to verification techniques, but are the result of designing for proofs, not performance. This thesis proposes a design for large files and in-memory caches that are amenable both to a high-performance implementation and proofs of correctness. It then describes their usage in VDFS, a verified high-performance file system with deferred durability guarantees. The evaluation of VDFS' performance shows that these additions measurably improve performance over previous verified file systems, and make VDFS competitive with unverified file system implementations. This thesis contributes implementation techniques for large files and in-memory caches that can be applied to increase performance of verified systems..