Big data service requires lots of IT resource if users want the fast analysis of big data. Thousands of CPUs, hundreds of tera-byte storages and very high speed interconnections are demanded. Therefore, it is necessary to find the economic way for the provisioning of IT resource for big data center. This paper tried to discover what the key player of service bottleneck is in big data center. Using NS2 simulator, the authors showed the dependency between some components of IT resource and service bottleneck and proposed the efficient way of the performance improvement for the big data center.