I got a new workstation. Intel Core i7 @2.67
When I render a scene now it just takes 18% of the cpu.
No other program is started.
When i use it with DR - the slave has 25% of cpu for max and the workstation only 13%.
If you have a lot of vray proxies in the scene you machine may be bottlenecked on too little ram. vray loads proxies into ram when a bucket hits a proxy, lots of buckets=lots of proxy which means you can get a lot of swapping from ram into virtual memory which slows everything down