Data replication is done on volumes with 16TB size or less, if you have let say a 80TB of storage, then you need to divide this to a 16TB volumes( that means 5 volumes for 80TB as an example ) so you can replicate each volume, and at the end replicate all the storage size you have. Sure you can create volumes with size less than 16TB if you need to.

__________________
Alaa Souqi