Given that virtual environments for x86 servers are relatively new, most lack direct experience in performing major in-place upgrades. While there are many ways to approach a key upgrade to a virtual environment, we’ll take a look at one example of a server virtualization upgrade: VMware ESX 3.5 and VirtualCenter 2.5 to the Update 1 release of both products. This release resolved some major issues, putting the spotlight back on the new features of ESX 3.5, namely Storage VMotion.
Maintaining version control on a virtualization platform is in the best interest of ongoing administration. With VMware environments, this situation is illustrated by the sequential upgrade tasks with older versions of ESX and VirtualCenter. The first step in making a successful upgrade is to go through the release notes and scour the Internet for existing resources that can make this task less daunting. One particularly helpful resource is the RTFM Education ESX and VirtualCenter upgrade guide by Mike Laverick which goes through many scenarios with specific, step-by-step guides on almost every topic of the upgrade.
Having all of the resources in the world may still not be enough to ensure a smooth upgrade of the virtual environment. This is where a test environment for the upgrades can prove critical to a successful project. Provisioning an accurate test environment can become increasingly expensive, but can provide a beneficial test ground to ensure there are no surprises during the upgrade. Consider the test environment shown in the figure below:
This test environment is a smaller, yet representative environment of the larger environment in that it may have the same storage system, base drivers on the host systems yet simply providing a smaller workload. This environment can be an adequate test environment for all of the basic functions involved with an upgrade. As for provisioning the environment, there are some tricks available such as using the systems in an unlicensed or evaluation mode, reducing processor inventories or taking resources from the live environment if the loss can be sustained.
Planning and testing are the best defenses against an upgrade failure. Furthermore, because the scope of a virtual environment is so broad, the investment in testing and planning should be a no-brainer.