Large clusters, like the Sun Constellation System, are designed to handle many thousands of jobs and hundreds of users. Although some applications have been developed to use thousands of cores, most use from 1 to 1024. I am sure that studies have been done on this, but lets assume that applications are running at this rather small scale. Each of the Sun Blade 6048 Chasis, when fully populated, holds from 768 to 1152 cores of x64 processing power. The TACC Ranger system has almost 65,000 cores. As the core density increases in each socket (currently up to 6 for x64 systems), the number of cores/cluster will continue to expand.

So how to control which application runs where ? Allowing each user to decide on which set of cores they want to run their application would create chaos, leading to inefficient usage of resource. You really dont want different application competing for the same core. Enter a Distributed Resource Manager (DRM), like the very popular Sun Grid Engine.

Sun Grid Engine 6.2 update 3 is currently available for download. SGE (as it is commonly known) is a distributed resource management  system is designed to maximize
resource utilization by matching incoming workload to available
resources according to the needs of the workload and the business
policies that are in place. Truly heterogeneous, it supports a large
number of platforms and operating system. SGE has many features, so it is very important to look at: www.sun.com/sge  .

Briefly, here is a diagram of how SGE works. Be sure to learn more about it, and increase your utilization of your cluster by using SGE. 

Source/Kaynak : http://blogs.sun.com/SunConstellationSystem/entry/i_want_my_cores_sun