From a service perspective, I have had the experience of delivering different vendor Hypervisors into a single customer environment. The original justification used by the customer was to reduce costs. What was quickly apparent though, is that the upfront cost benefit did not come anywhere near covering the increased operational costs and complexity experienced post deployment. In addition, neither one of the vendor management platforms was considered adequate by the customer; VMware's being exclusive and Microsoft's requiring integration of multiple solutions. Although Microsoft has gotten better, VMware is extremely good at managing their hypervisors. There was also a strong push back from the operational team once they experienced the management of a mixed hypervisor environment without a single targetted toolset to deal with both.
I suspect that the split in hypervisors happens as much for political reasons vs. real cost reduction. In the history of Virtual Desktop Infrastructure (VDI) the idea of having a server virtualization team manage desktops has typically been an under considered decision by IT teams. The server virtualization team is eager to approach the new technology but less eager to adopt desktop support. This is the stake that is wedging a 2nd hypervisor into the mix. IT teams force separation of servers and client side virtualization onto separate platforms to ensure ownership by one group or another.
The 2nd pressure I believe is cost justification. I recall being at a Financial firm when they introduced IBM blades in addition to HP blades to reduce costs. The capital costs savings was offset by the operational overhead in supporting the two platforms. As the support cost was a soft cost and not visible in a single bucket the executive 'cost cutting' decision carried the day and we became a dual platform environment. I believe that from an accounting perspective the organization did benefit from having two vendors in play when it came to renewal but the overhead was definitely felt by support.
When introducing an additional virtualization vendor you must consider what the true benefit is from running a mixed hypervisor environment?
- Cost; Capital vs. Operational?
- Should you have different hypervisors for virtual desktop and servers?
- What is the benefit of avoiding vendor Lock in?
What are the road blocks you will likely face in implementing a mixed hypervisor environment?
- Current Maturity of Toolsets
- Cost and benefits of having not just two hypervisors but perhaps an additional management platform
- Do your virtualization vendors provide a single point of management or is another software product required?
There can be many benefits to running a mixed mode environment. It is important to consider the decision carefully to avoid adding complexity without any return on the investment.