how to rebalance individual data node?

[Jim Donofrio]

Lets say that every node in your cluster has 2 same sized disks and one 
is 50% full and the other is 100% full. According to my understanding of 
the balancer documentation, all data nodes will be at the average 
utilization of 75% so no balancing will occur yet one hard drive in each 
node is struggling at capacity. Is there any way to run the balancer 
just on a datanode to force each disk to be 75% full?

Thanks