thanks for the input -- so yeah I saw the RAID5/6 thing. I'm wondering if it's a bit of a moot point, because the servers basically all come with 2 identical drives of various speed.

Moving writes to ARC or SLOG-on-a-faster-thing would also definitely help, but I'm dealing with SSDs for the most part.

Also, talking of faster storage, NVMe looks really bad for ZFS (and probably btrfs), based on this reddit post[0](graphs[1]). It's not terrible of course, and some recommended that maybe actually turning ARC off would be better, since it might have been actually getting in the way of the NVMe drive.

[0]: https://www.reddit.com/r/zfs/comments/jmdxxx/openzfs_benchma...

[1]: https://64.media.tumblr.com/0d141001aa951a44063c2cac9d2b9cb7...