Going to implement this right away to get into next versons.
Should probably go in StorageServiceMBean.
I couldn't assign this to myself, but here's a patch
If we could get this backported to 0.7 that would be awesome too..
Integrated in Cassandra-0.7 #529 (See https://builds.apache.org/job/Cassandra-0.7/529/)
Expose data_dir through JMX.
Patch by Mike Bulman, reviewed by brandonwilliams for CASSANDRA-2770
brandonwilliams : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1147248