2026-09-13 –, D.0.02
Earlier this year I conducted a performance investigation and tuning of a slow backup job. Essentially, a single rsync syncing a deeply nested directory tree with thousands of files over the network onto a ZFS dataset on a remote server.
After a reboot of the remote server, the backup would be received and saved on a local filesystem in about 10 minutes. Unfortunately, as the uptime grew the rsync would run for days on end instead of minutes.
During the talk I will share with you how I figured out where rsync's bottleneck was and what I did to make the syncing finish within the expected timeframe of 10 minutes. I will show you what tools I used during the investigation to discover what parts of the system are screaming for help and to verify my hypothesis of where the root cause is.
We will explore tuning of caching on FreeBSD, ZFS performance metrics, and using DTrace to get a closer look at system's internals.
That's all Folks!
Mateusz Piotrowski is a Systems Engineer based in Berlin, Germany. He has long contributed to open source, primarily to the FreeBSD and OpenZFS projects. He served on the FreeBSD Core Team from 2022 to 2024. Professionally, he consults companies on performance engineering and open-source development.