Broad general statements are always difficult but FWIW: - btrfs is fine if you want checksumming for your external HDD with some backup stuff that is mostly se

Broad general statements are always difficult but FWIW: - btrfs is fine if you want checksumming for your external HDD with some backup stuff that is mostly sequential i/o. - For everything else - especially anything that goes beyond a single disk use ZFS. btrfs RAID1 is not really raid1 but rather oddness of pid decides which drive to read from, raid5,6 had serious issues a while back - the write hole problem still exists for btrfs. ZFS stripe, mirror, raidz are well understood and work flawless afaik. btrfs also does strange things when replacing disks, like going read-only when one disk fails - at least it used to be that way. - performance is a mixed bag but broadly speaking for anything that is not sequential io on an empty disk btrfs is slower than other filesystems[1], for ZFS it depends can be slower or faster than ext4 depending on a lot of settings... - ZFS tooling is far superior to btrfs - I've used both a lot and you won't go back to btrfs tooling once you've used ZFS. - btrfs snapshots degrade performance with rising snapshot count. ZFS works fine. - ZFS has native encryption with zfs send / recv support in the upcoming 0.8.0. So you can do encrypted differential backups this way. - btrfs quota was for a long time broken and error-prone, not sure what the current status is but it never worked correctly for me. - ZFS lacks cp --reflink and linux pagecache integration as well as sendfile() on Linux and the ZFS ARC is independed of the pagecache - that has some consequences for e.g. mmap(). - ZVOLs are ZFS only you can create block devices as ZFS datasets i.e. zfs create -V 10G rpool/xfs && mkfs.xfs /dev/zvol/rpool/xfs && mount /mnt /dev/zvol/rpool/xfs can be useful for ceph, running docker on xfs volumes in container - btrfs works fine inside containers so you can run Docker in LXD/LXC - ZFS is not there yet - overlay2 support is also missing. - no io-scheduling via cgroups for ZFS afaik because the Linux queue subsystem is not used... - Last but not least: ZFS has ZIL & L2ARC. ZIL is huge for spinning disks because sync() writes are first written to an ssd storage and later async and sequential to the hdd. TL;DL: apt update and databases are fast even on spinning disks. L2ARC is an SSD-Cache but it's not so effective in my experience (low hitrate for typical hosting stuff) - Personally I will avoid using btrfs if I can. 1: https://www.phoronix.com/scan.php?page=article&item=freebsd-12-zfs&num=2 https://www.phoronix.com/scan.php?page=article&item=freebsd-... it's a little bit apples/oranges because ZFS Freebsd != Linux ZFS but IMHO it shows that the architecture/design is sound.