DFUSE: Strongly Consistent Write-Back Kernel Caching for Distributed Userspace File Systems

TL;DR

DFUSE addresses the challenge of achieving strong consistency in FUSE-based distributed file systems without sacrificing write-back kernel caching. By offloading distributed lease management into the kernel driver, DFUSE coordinates page-cache access across nodes, enabling high-throughput I/O with low latency while maintaining cluster-wide correctness. The design introduces kernel-level lease operations, a userspace buffer cache, a global file identifier, and a replicated lease manager, and demonstrates up to 68% higher throughput and 40.4% lower latency than write-through baselines, with near-linear scalability to 16 nodes. This approach significantly broadens the practical applicability of FUSE DFSs to write-intensive cloud workloads and demonstrates a viable path toward rapid, kernel-assisted coordination in distributed file systems.

Abstract

Cloud platforms host thousands of tenants that demand POSIX semantics, high throughput, and rapid evolution from their storage layer. Kernel-native distributed file systems supply raw speed, but their privileged code base couples every release to the kernel, widens the blast radius of crashes, and slows innovation. FUSE-based distributed file systems flip those trade-offs: they run in user space for fast deployment and strong fault isolation, yet the FUSE interface disables the kernel's write-back page cache whenever strong consistency is required. Practitioners must therefore choose between (i) weak consistency with fast write-back caching or (ii) strong consistency with slow write-through I/O, a limitation that has kept FUSE distributed file systems out of write-intensive cloud workloads. To this end, we present DFUSE, the first distributed FUSE file system that delivers write-back kernel caching and strong consistency. DFUSE achieves this by offloading userspace consistency control 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 strong consistency without compromising performance. In our evaluation, DFUSE achieves up to 68.0% higher throughput and 40.4% lower latency than the existing write-through design of FUSE-based distributed file systems.

Figures (9)

• Figure 1: Overview of the FUSE Framework
• Figure 2: Latency breakdown of write requests in FUSE
• Figure 3: Challenges of leveraging the write-back page cache in FUSE-based distributed file systems
• Figure 4: The overview of DFUSE
• Figure 5: DFS client components.