pFSCK: Accelerating File System Checking and Repair for Modern Storage

We propose and design pFSCK, a parallel file system checking and recovery (C/R) tool designed to exploit compute and storage parallelism in modern storage devices. pFSCK enables fine-grained parallelism at the granularity of inodes and directory blocks without impacting the C/R's correctness. pFSCK first employs data parallelism by identifying functional operations in each stage of the checking logic and then isolating dependent operations and shared data structures. However, full isolation of shared structures is infeasible and requires serialized updates. To reduce serialization bottlenecks, pFSCK introduces pipeline parallelism, allowing multiple stages of C/R to run concurrently without impacting correctness. Further, pFSCK provides per-thread I/O cache management, dynamic thread placement across C/R stages, and a resource-aware scheduler to reduce the impact of C/R on other applications sharing CPUs and the file system. Evaluation of pFSCK shows more than 2.6x gains over e2fsck (Ext file system C/R) and more than 1.8x over XFS's C/R that provides coarse-grained parallelism.