4 ms·

> I’ve used my two “usual” machines with different hardware configurations, a small one with SATA SSD and a bigger one with NVMe SSD. ZFS has some known limita

> I’ve used my two “usual” machines with different hardware configurations, a small one with SATA SSD and a bigger one with NVMe SSD. ZFS has some known limitations running on NVMe/flash. See Allan Jude's EuroBSDcon 2022 presentation "Scaling ZFS for NVMe": * https://registration.eurobsdcon.org/conferences/2022/program/proposals/220 https://registration.eurobsdcon.org/conferences/2022/program... * https://www.youtube.com/watch?v=v8sl8gj9UnA https://www.youtube.com/watch?v=v8sl8gj9UnA When ZFS was created spinning rust was still the main thing, and SSDs were just gaining popularity, so ZFS created "hybrid storage" pools to balance space, speed, and cost: * https://cacm.acm.org/magazines/2008/7/5377-flash-storage-memory/fulltext https://cacm.acm.org/magazines/2008/7/5377-flash-storage-mem... * https://web.archive.org/web/20080613124922/http://blogs.sun.com/jonathan/entry/not_a_flash_in_the https://web.archive.org/web/20080613124922/http://blogs.sun.... * https://web.archive.org/web/20080615042818/http://blogs.sun.com/ahl/entry/flash_hybrid_pools_and_future https://web.archive.org/web/20080615042818/http://blogs.sun.... * https://www.brendangregg.com/blog/2009-10-08/hybrid-storage-pool-top-speeds.html https://www.brendangregg.com/blog/2009-10-08/hybrid-storage-... * https://en.wikipedia.org/wiki/Hybrid_array https://en.wikipedia.org/wiki/Hybrid_array

pgaddict 3y ago
Yeah, I certainly understand ZFS was designed for different types of storage, but we now have flash storage as a default ... Which is why I do these benchmarks - to educate myself and learn what behavior to expect from different systems, and maybe even find stuff to optimize in Postgres. The goal definitely is not to "shame" some of the filesystems (or whatever I benchmark), I have huge respect to all of the engineers working on these things. FWIW I really like the ideas behind ZFS, and many deployments chose to use it. But that's kinda the point - to decide what's the right trade off you need to have some basic understanding what kind of behavior to expect.

pgaddict 3y ago

Yeah, I certainly understand ZFS was designed for different types of storage, but we now have flash storage as a default ... Which is why I do these benchmarks - to educate myself and learn what behavior to expect from different systems, and maybe even find stuff to optimize in Postgres. The goal definitely is not to "shame" some of the filesystems (or whatever I benchmark), I have huge respect to all of the engineers working on these things. FWIW I really like the ideas behind ZFS, and many deployments chose to use it. But that's kinda the point - to decide what's the right trade off you need to have some basic understanding what kind of behavior to expect.