If you’ve been running snapshots for a while and have already backed them up, you might occasional need to delete all zfs snapshots for your pool.
Typically, you’d do this as part of your backup script, assuming that they have been written correctly.
First, to find the used snapshot space, run this command:
zfs list -o space
This will give you a detailed readout of your pools and snapshot space used.
Here’s my script to wipe ZFS snap shots, but I am certainly open to suggestion:
zfs list -H -o name -t snapshot | xargs -n1 zfs destroy
Again, caution is needed as this will remove ALL SNAPS from your pools.