Question about HDFS allocations

[Bryan Duxbury]

We've been doing some testing with HBase, and one of the problems we  
ran into was that our machines are not homogenous in terms of disk  
capacity. A few of our machines only have 80gb drives, where the rest  
have 250s. As such, as the equal distribution of blocks went on,  
these smaller machines filled up first, completely overloading the  
drives, and came to a crashing halt. Since one of these machines was  
also the namenode, it broke the rest of the cluster.

What I'm wondering is if there should be a way to tell HDFS to only  
use something like 80% of available disk space before considering a  
machine full. Would this be a useful feature, or should we approach  
the problem from another angle, like using a separate HDFS data  
partition?

-Bryan