more replicas on a single node

[Ferdy Galema]

Is it possible to enforce a replication of 2 for a single node, so that 
replicas are spread out over disks? Currently with more replicas than 
nodes this results in "under-replicated" blocks. I understand that 
normally the best way to replicate is to span multiple machines for 
availabilty purposes. However is there a way around this?