created a volume with 2 dht bricks.added 3rd brick using add-brick. now kill 
glusterd and start glusted now add 4th brick.no errors found with add-brick and volume info- but 4th brick has no glusterfs process.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4thbrick#gluster peer probe 10.192.141.187
Probe successful

4thbrick#ps ax|grep glust
27856 ?        Ssl    1:09 /old_opt/3.0.4/sbin/glusterfsd -f /root/laks/cfg.vol /opt -l client.log -L NONE
30407 ?        Ssl    0:00 glusterd
30417 pts/0    R+     0:00 grep glust

~~~~~~~~~~~~~~~
10.192.141.187#gluster volume add-brick dht 10.198.110.16:/mnt/a1 
10.192.141.187#gluster volume info

Volume Name: dht
Type: Distribute
Status: Started
Number of Bricks: 4
Transport-type: tcp
Bricks:
Brick1: 10.192.134.144:/mnt/a1
Brick2: 10.192.141.187:/mnt/a1
Brick3: 10.214.231.112:/mnt/a1
Brick4: 10.198.110.16:/mnt/a1
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~