This appendix has described how to select the right hardware for your ArcGIS for Server environment by providing some rules of thumb. By calculating the number of cores and memory required to serve your users, you can now estimate the level of hardware you need to efficiently set up Server on a good hardware that can run comfortably and serve your users without experiencing any deficiencies or requiring upgrading frequently. The next appendix will explain the history of architectures of ArcGIS for Server 10.1 and 10.2 versus the prior versions 10 and 9.x.