Why is AWS more economical than traditional data centers for applications with varying compute workloads?
A. Amazon EC2 costs are billed on a monthly basis.
B. Users retain full administrative access to their Amazon EC2 instances.
C. Amazon EC2 instances can be launched on demand when needed.
D. Users can permanently run enough instances to handle peak workloads.
C
传统数据中心的运营，是全部或者部分基于物理服务器而构建的。各种各样的应用程序都是部署在这些传统的本地服务器上面。在部署应用程序之前，必须提前对应用程序所需的服务器容量做出决策，该决策一旦做出，购买的服务器容量在短期内保持固定。然而，由于应用程序的工作负载总是在不停地变动，
无论如何科学地进行容量决策，固定的服务器容量都很难恰好满足应用程序工作负载的需要。
当企业提供的应用程序会变的受客户欢迎的时候，需要购买更多的服务器以提供更高的负载能力。这些本地服务器价格非常昂贵，从购入之日开始就开始不断减值，直至最后报废被销毁。当这些应用程序变的空闲的时候，这些本地服务器也随之进入空闲状态，不能够产生任何价值，由此造成了昂贵的IT资产被严重浪费。
如果企业将应用程序部署在AWS上，当应用程序需要更高服务器容量的时候，用户可以手动或者自动地启动和终止相应的实例以响应变化的工作负载。因此这是一种比购买足够的本地服务器来处理峰值负载更经济的做法。
Six advantages of cloud computing
Stop guessing capacity – Eliminate guessing on your infrastructure capacity needs. When you make a capacity decision prior to deploying an application, you often end up either sitting on expensive idle resources or dealing with limited capacity. With cloud computing, these problems go away. You can access as much or as little capacity as you need, and scale up and down as required with only a few minutes’ notice.