Cool. zfs as of version 21 has deduplication built in. And thats the good dedup – synchronous dedup. i.e. deduped on the fly!
How easy is it to turn on? – very!
Once you have upgraded your zpool to 21 or above you can run the following command at the pool level and deduplication will be over all your data from that point onwards.
zpool set dedup=on tank
Note : Watch your performance, it will drop like a rock if you do not have enough ram for your dedup tables. Do some tests after enabling this feature.