Metadata
Abstract

Different storage technologies motivate the development of specialized file systems tailored to specific device types. A tiered file system aggregates such device types into a single file system. We argue that the current practice of developing tiered file systems tends to lag behind that of device-specific file systems because, inherently, developers are burdened with addressing multiple device types simultaneously, rather than specializing. We propose to solve this problem using Mux, a new tiered file system that accesses different device types indirectly through device-specific file systems, rather than directly through device drivers. Despite introducing an additional indirection layer, we show that Mux significantly outperforms Strata, a research tiered file system, because it utilizes specialized production-ready file systems. Compared with direct access to per-device file systems (with no tiering), Mux adds a worst-case read latency overhead of 6.6% to 87.3%, and a write throughout overhead of 1.6% to 3.5% across devices. We contend that Mux’s separation of tiering and specialization concerns enables progressive evolution and flexible integration of heterogeneous storage devices.

Citation

Jiyuan Zhang, Jongyul Kim, Chloe Alverti, Peizhe Liu, Weiwei Jia, and Tianyin Xu. “Rethinking Tiered Storage: Talk to File Systems, Not Device Drivers”. In Proceedings of the ACM SIGOPS 20th Workshop on Hot Topics in Operating Systems (HotOS), May 2025.