PDL ABSTRACT

Ext4-zcj: An Evolved Journal Optimized for Drive-Managed Shingled Magnetic Recording Disks

Carnegie Mellon University Parallel Data Lab Technical Report CMU-PDL-16-106. October 2016.

Abutalib Aghayev, Theodore Ts’o*, Garth Gibson, Peter Desnoyers^

Carnegie Mellon University
* Google Inc
^ Northeastern University

http://www.pdl.cmu.edu/

Drive-Managed SMR (Shingled Magnetic Recording) disks offer a plug-compatible higher-capacity replacement for conventional disks. For non-sequential workloads, these disks show bimodal behavior: after a short period of high throughput they enter a continuous period of low throughput. We introduce ext4-zcj, a small change to Linux ext4 file system that significantly improves the throughput in both modes. We present benchmarks on four different drive-managed SMR disks from two vendors, showing that ext4-zcj achieves 1.7-4.9X improvement over ext4 on a file server benchmark; on metadata-heavy benchmarks it achieves 2-13X improvement over ext4 on drive-managed SMR disks as well as on conventional disks.

KEYWORDS: Shingled Magnetic Recording, Linux, ext4, journaling, file systems

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