@Guy Riems Please read this: https://community.hortonworks.com/questions/89641/disk-size-used-is-bigger-than-replication-number-m.html#answer-89728 To know what is available, what you need is the number of blocks unused and multiply that with the size of the block. If your replication factor is 3 then quantify the number of blocks unused x size/block in all your data nodes and divide by three. To know what is used, it is the same: number of blocks used x size/block, but your blocks are most likely at < 100% ... +++ If this helped, please vote/accept as best answer. ... View more