I'm feeling bold today, so here it is. There are no remaining technical barriers to virtualizing your entire data-center. The benefits are real. What are you waiting for?
Many many customers have virtualized all the most business critical and performance intensive apps found in datacenters. Exchange is now commonly virtualized. SQL Server and Oracle databases are also run as VMs on vSphere in data centers all over the world. Even bigger more complex stuff like SAP and Oracle RAC can be run virtualized with no technical issues. There are proven examples for just about every application type out there. It works.
The benefits are big and from what I have seen, the more that you virtualize the bigger the benefits become. I think that everybody is aware of the clear consolidation benefit for legacy and underused servers. Once you have completed a consolidation effort you begin to see that the operational benefits are much bigger than what you realized before starting. In fact I would say that these benefits are much bigger than the pure consolidation gains.
The number of workloads that cannot be virtualized due to technical barriers is very small. This leaves issues like application licensing uncertainty, organizational politics, out dated conceptions of what virtualization can do, support questions, fear of change, and others. Some of these have simple answers and others are more difficult, but even though they are not technical reasons they are still very real reasons.
If you were to purchase a new Intel or AMD based server today with either two or four sockets, you would be hard pressed to find an application that truly needs the whole host. The only practical way to really utilize these nice new servers is to use virtualization to be able to run multiple workloads on it at the same time. Otherwise you are looking at a system that is probably less than 30% utilized almost all of the time.
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