note the solution to the rebalancing problem

howto/ganeti.md

@@ -805,8 +805,9 @@ move operations altogether.
 
 Both workarounds obviously do not correctly balance the
 cluster... Note that we have also tried to use `htools:migration` tags
-to workaround that issue, but [those do not seem to work correctly
-either](https://github.com/ganeti/ganeti/issues/1497).
+to workaround that issue, but [those do not work for secondary
+instances](https://github.com/ganeti/ganeti/issues/1497). For this we would need to setup [node groups](http://docs.ganeti.org/ganeti/current/html/man-gnt-group.html)
+instead.
 
 ## Adding and removing addresses on instances