When we allocate space to an LVM snapshot, the COW data is written to that space and then when that space is used up the LVM snapshot must either be given more space or must be deleted.

When a ZFS snapshot is marked, then changes to existing blocks in the snapshot as well as new writes all go to free space in the disk. There is no pre-allocated space within which these COW changes are written to.

Thus, we could have a single ZFS snapshot marked today followed by years of data being written to. This is not the intent of an LVM snapshot and the warning that I had quoted above is worth reviewing once.