Best Practices for OpenZFS L2ARC in the Era of NVMe

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Wednesday, September 25, 2019
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The ZFS L2ARC is now more than 10 years old. Over that time, a lot of secret incantations and tribal knowledge have been created by users, testers, developers, and the odd sales or marketing person. That collection of community wisdom informs the use and/or tuning of ZFS L2ARC for certain IO profiles, dataset sizes, server class, share protocols, and device types. In this talk, we will review a case study in which we tested a few of these L2ARC myths on an NVMe-capable OpenZFS storage appliance. Can high-speed NVMe flash devices keep L2ARC relevant in the face of ever-increasing memory capacity for ARC (primary cache) and all-flash storage pools?