Cloud Computing adoption is taking off. Two of the major principles of Cloud are: (1) resource pooling through mulitenancy (2)Elasticity. Multitenancy is the ability to have a single resource serves multiple clients. Example in Cloud is having multiple customers served by the same physical server. Elasticity is the ability to add or plug-in resources, fairly dynamically, to scale the server up or to scale down. For example, swapping in CPU, memory, disk space, etc.
Both of these principles are reliant on virtualization, the ability to run multiple, independent instances of software or hardware within a resource that was originally designed for a single use. The best example is a Server hosting multiple, independent operating systems that each are performing seperatlely from each other.
The leading vendor in the virtualization space is clearly VmWare. VmWare has been around the longest, and has the greatest market footprint, and has the most efficient use of hypervisor. Challengers in virtulaization space include Oracle, Microsoft, and few others.
The problem with VmWare, or the elephant in the room to speak of, is the # of enterprise software products that are still not supported on VmWare, namely Oracle. The largest example is Oracle, since they are the leader in enterprise software. Oracle software is only supported on Oracle's own product-- Oracle VM. Now, I do know there are a lot of customers running Oracle databases and Oracle middleware on VmWare and haven't had any issues yet. But, if there is an issue, these customers must understand their environment configured with VmWare is not supported by Oracle, Inc. You will be required to reproduce your issue in a non-VmWare environment OR on Oracle's VM software to get bug and issue support. This is scary, especially the number of customers I know who run Oracle on VmWare. Just the sheer possibility of losing production data or having long system downtime due to a non support issue, and then having to reproduce the entire environment to get support is enough risk for me take a strong look at Oracle VM so not to impact my Production systems. However, I'm no dummy and realize a lot of customers are running on VmWare just fine and haven't seen any issues, yet. I'd ask how advanced or complex their environement is? Are they doing RAC, Clustering, Load Balancing, Data Replication, or other advanced configurations? All of these could add complexity and impact the environment on a virtualization architecture. High performing applications that require this level of configuration could be risky in a VmWare environment, especially since VmWare does its own version of memory management, throwing off software like Oracle that manages its own SGA and PGA structures. Huge considerations for any customer thinking about virutalization-- lack of vendor support is serious stuff even if you think it works ok.
A second consideration is cost savings. This is one of the main drivers for virtualization. Squeeze more out of my existing resources instead of using it for a single purpose. For example, if I buy a physical server and its CPU and memory is very underutilized, then I can virtualize more Operating Systems onto the server and use the server for multiple purposes. This is good for hardware savings and not having to procure more hardware for your software applications, but won't buy you anything with your software licensing savings. the large software companies are very aware of this, and they will not give you a break on your software for putting more on a single resource. This is why they will not allow tools like VmWare to emulate the CPU's to make the customer's licensing less expensive.
I know VmWare has lots of examples where software on their product runs issue-free. This is great and I applaud the fact that it should work ok in a basic configured environement. However, VmWare cannot control the other software vendors like Oracle. I would ask to please get Oracle products officially supported on VmWare, and then we can all rest easier at night.
So, Big Elephant in the room-- to VmWare or not VmWare? No virtualziation, clearly makes a "Cloud Environment" difficult to achieve, especially losing multitenancy and elasticity principles. So, your first option is to ask your vendor what their policy is on virtualization support. If its a company like Oracle, consider using their Oracle VM product if you still need virutalization. VmWare may be your corporate standard for virtualization, but its not supported, and that is enough risk to avoid it until it is fully supported.