hadoop配置 - using the other hard disks

I've got a small cluster of 3 nodes with 5 x 2 TB hard drives in each computer.
All are running Ubuntu, have the same hardware specs, and are using Apache Hadoop 1.0.4.
The hard disks are mounted as /media/diskb, /media/diskc, /media/diskd, etc. on each respective computer and are configured as JBOD.

All 3 computers are serving as Data Nodes and Task Trackers, while one is the master Name Node and Secondary Name Node,
the 2nd is the Job Tracker, and the 3rd is a pure slave (DT/TT) node.

In each computer's hdfs-site.xml file, I have listed the mount points, comma-separated, no spaces as values.

<property> <name>dfs.data.dir</name> <value>/data/dfs/data,/media/diskb/data/dfs/data,/media/diskc/data/dfs/data,..</value></property>

For the Name Node:

<property> <name>dfs.name.dir</name> <value>/data/dfs/name,/media/diskb/data/dfs/name,/media/diskc/data/dfs/name,..</value></property>

In mapred-site.xml:

<property> <name>mapred.local.dir</name> <value>/data/mapred/local,/media/diskb/data/mapred/local,/media/diskc/data/mapred/local,...</value></property>

Also, in core-site.xml

<property> <name>hadoop.tmp.dir</name> <value>/media/diskb/data</value></property>

(I've played around with changing the temp directory to be assigned to a disk at a time to check permissions, etc and Hadoop works fine)

Permissions for the mounts and ownership of the directories are full for the Hadoop user account.
When I run a map/reduce program, I can see Hadoop create resource folders inside the extra disks on each node under their mapred/local directories,
and I can see the same happening for the data node directories and the configured capacity reported on the administration page (namenode:50070).