Data centers are the backbone of the variety internet services such as web-hosting, e-commerce, and social networking. Business relying on the DC services is showing an increasing and DC operators facing challenges to manage the DC resources. In order to cater the increase demand, DC operators are installing additional equipment in the DC. Thus, many research have highlighted the increasing trend of energy consumption in DC originates from the IT systems such as server, storage, network and from the non-IT system such as cooling system and power system. Looking into IT system, one of the solutions that may reduce the energy consumption in the DC is to adopt the Green Data Center using the green computing. However, DC operators are facing many issues and challenges and the most discussed in the literature are reliability and performance, resource management and energy management. This paper reviews the issues and challenges on the IT systems and to adopt the Green Data Center to assist DC operators moving towards the Green Data Center.