I do know that if you have very fast NVMe SSDs (>6000MB/s or so) ZFS is not currently able to give you the whole performance, due to time spent memcpying to/fro

I do know that if you have very fast NVMe SSDs (>6000MB/s or so) ZFS is not currently able to give you the whole performance, due to time spent memcpying to/from the ARC[0]. Direct IO support could eventually alleviate this[1]. [0]: https://github.com/openzfs/zfs/issues/8381 https://github.com/openzfs/zfs/issues/8381 [1]: https://github.com/openzfs/zfs/pull/10018 https://github.com/openzfs/zfs/pull/10018