OpenZFS 2.3.0 will be released any day now, and it includes the new “Fast Dedup” feature. My team at Klara spent many months in 2023 and 2024 working on it, and we reckon it’s pretty good, a huge step up from the old dedup as well as being a solid base for further improvements. I’ve been watching various forums and mailing lists since it was announced, and the thing I kept seeing was people saying something like “it has the same problems as the old dedup; needs too much memory, nukes your performance”. While that was true (ish), and is now significantly less true, the real problem is that this just repeating the same old non-information that they probably heard from someone else repeating it.