We investigate dynamic protection of cloud services supported by geo-distributed DCs (Geographically distributed Data Centers) under disaster scenarios which lead to failures of DC nodes and communication fibers. By assuming that the affected network region can be aware of an upcoming disaster for a certain early warning time before it is finally hit, and the corresponding service requests can be identified before they are disrupted, we utilize early warning time to achieve dynamic service protection by carrying out three methods: request rerouting, request relocation and service relocation. In particular, the first one reroutes requests to their original service providing DC nodes; the second one relocates requests to other service providing DC nodes; and the third one relocates requested services to backup DC nodes to support service requests. We first formulate an Integer Linear Program (ILP) model to maximize the number of disaster-affected requests that can be protected, and then propose a time-efficient heuristic solution. Extensive numerical results show that the proposed strategy can achieve good performance to protect service requests under disasters with early warning times.

我们研究在灾难情况下由地理分布的DC（地理分布的数据中心）支持的云服务的动态保护，这会导致DC节点和通信光纤的故障。通过假设受影响的网络区域可以在最终受到打击之前的某个预警时间内了解到即将发生的灾难，并且可以在中断之前识别出相应的服务请求，我们利用预警时间来通过以下方式实现动态服务保护：执行三种方法：请求重新路由，请求重定位和服务重定位。特别是，第一个将请求重新路由到其原始服务提供DC节点；第二个将请求重定位到其他服务提供DC节点；第三部分将请求的服务重定位到备用DC节点以支持服务请求。我们首先制定一个整数线性程序（ILP）模型，以使可以保护的受灾难影响的请求数量最大化，然后提出一种省时的启发式解决方案。大量的数值结果表明，所提出的策略可以在预警时间短的情况下达到良好的性能，从而在灾难情况下保护服务请求。