Enabling the Write-Back Page Cache with Strong Consistency in Distributed Userspace File Systems

Abstract: The large-scale, multi-tenant nature of cloud computing requires distributed file systems that offer stability, adaptability, and compatibility. FUSE-based distributed file systems have emerged as a popular solution for the cloud, offering fast deployment, fault isolation, and POSIX compliance. However, FUSE's performance limitations, particularly its inability to reconcile page caching with strong consistency in distributed environments, remain a persistent problem. Existing approaches either sacrifice consistency for performance or rely on inefficient caching, limiting their practicality. To this end, we present DistFUSE, the first FUSE-based distributed file system that relies on a write-back kernel-based page cache for performance and provides strong consistency. DistFUSE achieves this by offloading userspace lock management to the kernel driver, allowing coordinated access to the kernel's page cache across nodes. This design eliminates blind local cache updates and ensures cluster-wide consistency without compromising performance. Our evaluation shows DistFUSE improves throughput by up to 75% compared to baseline approaches.