The one thing that ZFS cannot do is defragment a pool. There are abuse patterns that are toxic for ZFS pools (and all other filesystems). Btrfs appears to be a

The one thing that ZFS cannot do is defragment a pool. There are abuse patterns that are toxic for ZFS pools (and all other filesystems). Btrfs appears to be able to repair this damage. https://tim.cexx.org/?p=1236 https://tim.cexx.org/?p=1236 https://www.usenix.org/system/files/login/articles/login_summer17_02_conway.pdf https://www.usenix.org/system/files/login/articles/login_sum...