Hey mastax, thanks for the notes. I'm no expert but want to respond to the following: 1. AFAIK none of these parts of the stack (postgres, ZFS) are using async

Hey mastax, thanks for the notes. I'm no expert but want to respond to the following: 1. AFAIK none of these parts of the stack (postgres, ZFS) are using asynchronous IO or Direct IO -- postgres doesn't support either, and ZFS supports async writes (that concept means something very specific in ZFS land), and ZFS doesn't support direct IO (though it comes up a lot). 2. See my response to 1 3. All my testing is actually on NVMe, and comparing the performance to mdraid/ext4 (I also tried LVM) it's actually pretty decent. People have been running databases on ZFS with great success for years and I'm quite possibly the least knowledgeable person who's written about it! You can be productive without O_DIRECT support (again Postgres doesn't use direct IO so). Absolutely worth the benefits that ZFS provides, in my mind.