ZFS has no room for configuration errors. A common critical mistake that required making a new pool was to add a non-redundant vdev to a redundant pool, as vdev

ZFS has no room for configuration errors. A common critical mistake that required making a new pool was to add a non-redundant vdev to a redundant pool, as vdevs could not be removed from pools, permanently rendering this pool non-redundant due to its weakest link. IIRC, the ability to remove a vdev has just recently been added as a feature for ZFS-on-Linux on master, but I do not believe it is released yet.