Business continuity is an important consideration in system design, including both system failures and datacenter destruction scenarios—and everything in between. Traditional system recovery documentation provides instructions for rebuilding a system using the hardware which is no longer accessible or operational. The problem is that there are usually no guarantees your disaster recovery or hardware vendors will be able to duplicate the original hardware.
Using different hardware can result in extended rebuild times as you struggle to understand why your applications do not function. Even if you can get the same hardware, you need to rebuild the environment from the ground up.
Finally, interruptions in business processes occasionally happen when systems are brought down for maintenance. You understand the necessity, but your users seldom do.
Virtualization provides advantages over traditional recovery methods, including:
» Breaking hardware dependency. Since the hypervisor provides an abstraction layer between the operating environment and the underlying hardware, you do not need to duplicate failed hardware to restore critical processes.
» Increased server portability. If you create virtual images of your critical system servers, it does not matter what hardware you use to recover from a failure—as long as the recovery server supports your hypervisor and, if necessary, the load of multiple child partitions. Enhanced portability extends to recovering critical systems at your recovery test site, using whatever hypervisor-compatible hardware is available.
» Elimination of sever downtime (almost). You may never reach the point at which maintenance downtime is eliminated, but virtualization can get you very, very close. Because of increased server portability, you can shift critical virtual servers to other devices while you perform maintenance on the production hardware. You can also patch or upgrade one partition without affecting other partitions. One way to accomplish this is via clustering, failing over from one VM to another in the same cluster. From the client perspective, there is no interruption in service—even during business hours.
» Quick recovery of end-user devices. When a datacenter goes, the offices in the same building often go as well. Further, satellite facilities can suffer catastrophic events requiring a complete infrastructure rebuild. The ability to deliver desktop operating environments via a centrally managed virtualization solution can significantly reduce recovery time.
It might seem that virtualization is an IT panacea. It is true that it can solve many problems, but it also introduces new challenges.
Source of Information : Elsevier-Microsoft Virtualization Master Microsoft Server Desktop Application and Presentation