Hi Umesh,
Since some time SAP has inceased its porfolio of could solutions. Some are specific solutions that are clould based such as Success Factors or Ariba, but combinations are possible as well where customers have an on-site ERP in combination with a cloud based solution.
http://www54.sap.com/pc/tech/cloud.html
It is also possible to have the full ERP solution in the cloud. There are different tools to access these could solutions (e.g. Fluidops). Do you plan to just run SAP RE-FX in a virtual environment without the other SAP modules?
Regards, Andre