Server virtualization presents interesting implications for disaster recovery (DR), including cost reductions and increased recovery times. 

How does server virtualization improve recovery times?

With traditional tape systems it can take one to two days to completely restore a system. Server virtualization can reduce full restoration to four hours or less because it’s not necessary to rebuild servers, applications or operating systems separately. They exist elsewhere and can be brought back online.

What is critical is ensuring that the systems are regularly monitored so that they're in place and up to date. It's a useful way to perform disaster recovery testing because you can run a test on the virtual image of the system without affecting your production system. 

Effective server virtualization approaches for disaster recovery

Virtualization is performed with hardware, software or a combination of both. The key issue in terms of disaster recovery is to determine how many servers you're going to need to back up and create a full image of all the information.

This is called the server consolidation ratio, which is basically the number of virtual machines a server can host. While you can look at your inventory of servers and other related technologies, be careful not to reduce the number of servers too far so you can recover and restore critical applications and operating systems.  

How to determine what systems in your business need to be virtualized  

First, look at applications and operating systems that are most crucial to the business. Email is one of the most important applications and Microsoft Office is crucial as well. However Microsoft Office may be implemented on individual systems.  

The primary goal is to protect email and other critical applications, as well as any specialized applications that were developed in-house and cannot be easily recreated.

Major products that facilitate disaster recovery in a server virtualization environment  

From a software perspective, VMware Inc. is probably the largest vendor of products and services. ESX Server and VMware Server are both very popular. A lot of organizations leverage partitioning capabilities from their mainframe environment into a virtualization option.

The role of failover and failback in a server virtualization environment  

Failover is the ability to switch over to a redundant or standby server, system or network if an existing asset fails. It should happen without any kind of human intervention or warning. This contrasts with switchover, where you're dynamically making a transition from one environment to another.

Failback is the process of restoring a system or another asset that's in a failover state back to its original state. The assumption there is that you're able to bring it back to the state of operation before the disruption.

With a virtualized environment, you can failover to the environment, which exists in real time, and it's very easy to failback to the original mode because you can maintain images of your previous environments. What's nice about this is that it speeds recovery time and it's possible to do testing on an actual system without adversely affecting your actual production environment.  

Disaster recovery planning in a virtualized environment
When you're doing disaster planning, look at backing up critical data. You may be using tape, RAID or disk technologies, but access to a virtual environment must be factored in when you're developing your DR plan. This will provide excellent control over where your emergency resources are located.

Additionally, you’ll be able to justify the value of disaster recovery because as you're reducing your footprint, you're also increasing and improving your ability to recover in any kind of emergency. Disaster recovery, in conjunction with a virtualized environment, can go a long way in proving the ROI of your virtualization strategy.

Plan your disaster recovery strategy.