Uploaded September 2025 | Updated September 2026, 2 hours ago
ZFS Direct IO Benchmarking Pitfalls by Mateusz Piotrowski
Not too long ago, support for direct IO landed in OpenZFS after years of discussions and reviews. We truly live in the future where we can finally reject complicated caching and fully embrace the unbuffered conversations with our disks. Or can we really?
Those of you who know a bit about ZFS know that the ARC is actually pretty important (without one ZFS would historically stand for zzz 😴 instead of Zetta). How could it be then that skipping the ARC might improve performance?
During the presentation we will discuss what workloads and setups benefit from direct IO, what its limitations are, and what pitfalls to avoid during benchmarking. We will also look at the implementation to understand how all the promises of stability and compatibility were kept.
Direct IO is reported to deliver amazing performance boosts in some deployments. Understanding how not to hold it wrong is a great first step to potentially unlocking that speed-up on your systems too!
For more information, please visit:
bsdcan.org/2025
- and -
bsdcan.org/2025/timetable/timetable-ZFS-Direct-IO.html
#zfs #benchmarking #freebsd
ZFS Direct IO Benchmarking Pitfalls by Mateusz Piotrowski
Not too long ago, support for direct IO landed in OpenZFS after years of discussions and reviews. We truly live in the future where we can finally reject complicated caching and fully embrace the unbuffered conversations with our disks. Or can we really?
Those of you who know a bit about ZFS know that the ARC is actually pretty important (without one ZFS would historically stand for zzz 😴 instead of Zetta). How could it be then that skipping the ARC might improve performance?
During the presentation we will discuss what workloads and setups benefit from direct IO, what its limitations are, and what pitfalls to avoid during benchmarking. We will also look at the implementation to understand how all the promises of stability and compatibility were kept.
Direct IO is reported to deliver amazing performance boosts in some deployments. Understanding how not to hold it wrong is a great first step to potentially unlocking that speed-up on your systems too!
For more information, please visit:
bsdcan.org/2025
- and -
bsdcan.org/2025/timetable/timetable-ZFS-Direct-IO.html
#zfs #benchmarking #freebsd
