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Tuesday, July 9 • 11:10am - 11:40am
Filesystem Aging: It’s more Usage than Fullness

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Filesystem fragmentation is a first-order performance problem that has been the target of many heuristic and algorithmic approaches. Real-world application benchmarks show that common filesystem operations cause many filesystems to fragment over time, a phenomenon known as filesystem aging.

This paper examines the common assumption that space pressure will exacerbate fragmentation. Our microbenchmarks show that space pressure can cause a substantial amount of inter-file and intra-file fragmentation. However, on a “real-world” application benchmark, space pressure causes fragmentation that slows subsequent reads by only 20% on ext4, relative to the amount of fragmentation that would occur on a file system with abundant space. The other file systems show negligible additional degradation under space pressure.

Our results suggest that the effect of free-space fragmentation on read performance is best described as accelerating the filesystem aging process. The effect on write performance is non-existent in some cases, and, in most cases, an order of magnitude smaller than the read degradation from fragmentation cause by normal usage.


Alex Conway

Rutgers University

Eric Knorr

Rutgers University

Yizheng Jiao

The University of North Carolina at Chapel Hill

Michael A. Bender

Stony Brook University

William Jannen

Williams College

Rob Johnson

VMware Research

Donald Porter

The University of North Carolina at Chapel Hill

Martin Farach-Colton

Rutgers University

Tuesday July 9, 2019 11:10am - 11:40am PDT
HotStorage: Grand Ballroom I–III