4 1. Introducing 1.uNderstanding the Layers of High Availability o Even in non-virtualized environments, there are multiple ways to achieve high availability for Operating System(OS)instances and applications. When you introduce virtualization into the mix with VSphere, you gain additional methods of providing high availability At each layer are tools and techniques for providing high availability and business continuity o The virtualization layer offers a number of features for high availability, including vSphere High Availability(HA), vSphere Fault Tolerance(FT), and stretched(metro) storage clusters At the Physical layer, high availability is achieved through redundant hardware--multiple network interface cards(NICs) or host bus adapters (HBAs), multiple storage area network(SAN) switches and fabrics, multiple paths to storage, multiple controllers in storage arrays, redundant power supplies, and so forth 河南中医药大学/阮晓龙/13938213680/htp/cloudxg.hactcm.edu.cn/http:/www5ucwebcn