[root@nixos:~]# zfs list
NAME                 USED  AVAIL  REFER  MOUNTPOINT
backup              1.10M   899G   176K  none
backup/uranus        176K   899G   176K  none
backup/venus         176K   899G   176K  none
venus                217G     0B   176K  none
venus/home           384M     0B   384M  legacy
venus/redmond        110G  68.0G  42.3G  -
venus/root          66.8G     0B  66.8G  legacy
venus/storage       20.8G     0B   176K  none
venus/storage/data  16.7G  8.50G  8.17G  -
venus/storage/swap  4.17G  2.13G  2.04G  -
venus/swap          18.6G  17.0G  1.57G  -

[root@nixos:~]# zfs destroy -r venus@2019-05-13

[root@nixos:~]# zfs list
NAME                 USED  AVAIL  REFER  MOUNTPOINT
backup              1.10M   899G   176K  none
backup/uranus        176K   899G   176K  none
backup/venus         176K   899G   176K  none
venus                163G  52.2G   176K  none
venus/home           384M  52.2G   384M  legacy
venus/redmond       68.0G  78.0G  42.3G  -
venus/root          66.8G  52.2G  66.8G  legacy
venus/storage       10.6G  52.2G   176K  none
venus/storage/data  8.50G  52.6G  8.17G  -
venus/storage/swap  2.13G  52.3G  2.04G  -
venus/swap          17.0G  67.7G  1.57G  -

[root@nixos:~]# zfs set refreservation=none venus/redmond

[root@nixos:~]# zfs snapshot -r venus@2019-05-13

[root@nixos:~]# zfs list
NAME                 USED  AVAIL  REFER  MOUNTPOINT
backup              1.10M   899G   176K  none
backup/uranus        176K   899G   176K  none
backup/venus         176K   899G   176K  none
venus                149G  66.2G   176K  none
venus/home           384M  66.2G   384M  legacy
venus/redmond       42.3G  66.2G  42.3G  -
venus/root          66.8G  66.2G  66.8G  legacy
venus/storage       20.8G  66.2G   176K  none
venus/storage/data  16.7G  74.7G  8.17G  -
venus/storage/swap  4.17G  68.3G  2.04G  -
venus/swap          18.6G  83.2G  1.57G  -

[root@nixos:~]# zfs send -R venus@2019-05-13 > /dev/null
^C