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What are the differences between the VMware and Hyper-V hypervisors?
For years, VMware was the only sensible choice for enterprise-class server virtualization. However, Microsoft has recently made drastic improvements to Hyper-V in Windows Server 2012 and the forthcoming Windows Server 2012 R2. As such, it seems prudent to explore the question of using VMware versus Hyper-V in your environment and the differences between these two hypervisors.
Let me say up front that both VMware Inc. and Microsoft offer highly capable solutions. Both companies have products for small shops, but also sell products with features suitable for the largest enterprise environments. In fact, VMware and Hyper-V have an extremely comparable feature set. Both products offer roughly the same core feature set and support capabilities such as network virtualization, virtual machine (VM) migration, storage migration and network interface card teaming.
Although the two hypervisors have similar feature sets, feature capabilities are often somewhat different. Take Dynamic Memory, for example. Both hypervisors dynamically adjust physical memory usage according to the needs of the guest operating system (OS). The difference is that VMware offers Dynamic Memory support for any guest OS, while Hyper-V has historically supported Dynamic Memory only for VMs that are running Windows. However, Microsoft is adding Dynamic Memory support for Linux VMs in Windows Server 2012 R2 Hyper-V.
There are also significant differences in the VMware versus Hyper-V hypervisors in terms of scalability. Hyper-V hosts can support up to 320 logical processors, as opposed to VMware's 160. Similarly, Hyper-V servers can address up to 4 TB of RAM, whereas VMware vSphere 5.1 Enterprise Plus is only able to address 2 TB of RAM.
Hyper-V also offers greater scalability at the cluster level than VMware does. A Hyper-V cluster can include up to 63 nodes and support up to 8,000 VMs, with a maximum of 1,024 active VMs on any given host. In contrast, VMware clusters can include up to 32 nodes and support a maximum of 3,000 VMs per cluster (with a maximum of 512 active VMs per host).
While it's true that Hyper-V has VMware beat in terms of hypervisor scalability, it's important to consider the ways in which hypervisors are used in the real world. Many large organizations have found it more useful to create multiple clusters of a relatively small size rather than trying to build hyper-scaled clusters. Smaller clusters tend to be easier to manage, and having several small clusters rather than a single large one helps to mitigate some of the effects of a cluster-level failure. This isn't to say that Microsoft's hypervisor scalability isn't impressive or useful, but rather that right now there aren't many organizations taking full advantage of it.
Another major difference between VMware and Hyper-V is the way products are licensed. Microsoft includes Hyper-V with Windows Server 2012. A single Datacenter Edition license is valid for up to two CPU cores and allows for an unlimited number of VMs running on the host. As an added bonus, the Datacenter Edition license allows each VM running on the host to run Windows Server 2012 without requiring an extra OS license.
It's also worth noting that all of Hyper-V's core capabilities are included with a Windows Server license. You don't have to pay extra to use features such as Live Migration. In contrast, some of the VMware features come at a premium price.
Microsoft also takes a more simplified approach to its products. As previously mentioned, Hyper-V is included with Windows Server 2012. Larger organizations that require enterprise management capabilities will also likely need System Center 2012 Virtual Machine Manager. However, that is pretty much the extent of Microsoft's Hyper-V offerings.
In contrast, VMware offers dozens of different products (or product variations). On one hand, this means VMware can offer its customers extreme granularity by giving them the exact features and capabilities they need. On the other hand, there are so many different products to choose from that it can be difficult for an inexperienced administrator to know which products to purchase.
So which is better, VMware or Hyper-V? Both VMware and Microsoft have compelling arguments as to why their respective products are the best. Feature-wise, I think the two products are too similar to one another for me to definitively declare one product as the best. Besides, there are other criteria to consider beyond the feature set. For instance, VMware is a more mature product and there are more third-party products designed to work with VMware than Hyper-V. Conversely, it's often far less expensive to deploy Hyper-V than VMware (but not always).
About the expert:
Brien Posey is a Microsoft MVP with two decades of IT experience. Before becoming a freelance technical writer, Brien worked as a CIO for a national chain of hospitals and healthcare facilities. He has also served as a network administrator for some of the nation's largest insurance companies and for the Department of Defense at Fort Knox.
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