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Hyper-converged infrastructure virtualizes all of the resources in an IT system to allow for easier and more efficient deployment of virtual machines. The hypervisor software is the key to managing the virtualized storage, compute and networking resources, as well as the virtual machines that use them.
There are many factors to consider when choosing the HCI system and the hypervisor that is a part of it.
Hypervisor: A product or a feature?
Is your hypervisor a product or a feature of a product? The simple and not very helpful answer is both. For example, you can buy the hypervisor software ESXi from VMware as a standalone product, but to get the most out of it, you would need to match it with other VMware products. After all, it is designed to work best as part of the overall vSphere suite.
Because hypervisors are designed to work best as a functioning part of a greater whole, vendors would like you to think of them as features that simply come with the larger suite of HCI software. This is certainly the stance of the HCI vendors that use ESXi or Hyper-V in their customized hyper-converged products. For them, there is no other way for the buyer to see the hypervisor in their software set or appliance than as a feature and not a separate product. And if you like the appeal of an HCI appliance, you probably don't care much about the hypervisor -- just that it's there.
How important is proper planning?
Choosing the hypervisor software to use with your HCI deployment begins with choosing the right HCI product and vendor. To do that, you need to determine which vendor can best meet your current and future needs. You must analyze end users' current compute and storage use patterns. You must then analyze how those patterns have changed over time and how your company's planned growth will affect that change. That will give you a sense of how many virtual machines (VMs) you currently need and what the compute and storage makeup of the HCI system will look like when you deploy it. It will also give you a sense of the rate at which you will add VMs in the future so you can pick the best HCI product to meet that growth rate.
Should you match hardware and hypervisor?
If you plan to build your own HCI system, it is vital to make sure that the various components match the hardware you will install them on. Even if you opt to buy a software-only HCI platform and put it on your own hardware, you should match hardware capabilities to the software needs.
For example, if your plans account for a certain number of VMs with a predetermined amount of growth per quarter or year, it is important to purchase hardware that makes the most financial sense for that kind of growth pattern. It is also important to pick the hypervisor software that best fits that level of growth, although nearly all types are flexible enough to expand in very small to very large increments.
Custom or off-the-shelf?
If you plan to build your HCI system in-house, your only choice is an off-the-shelf (OTS) hypervisor -- that is, assuming you don't have an in-house development genius capable of building one. OTS hypervisors include ESXi from VMware, Hyper-V from Microsoft and open source products, such as Kernel-based Virtual Machine.
One advantage of buying OTS is flexibility. Again, assuming you have the IT staff capable of doing so, you can modify a hypervisor to meet the exact needs of your HCI deployment.
Using a custom-built, device-specific hypervisor as part of an inclusive HCI package generally is less expensive and easier to use than an OTS option. By customizing the hypervisor to work with other HCI components, the vendor can eliminate unnecessary or redundant features found in OTS hypervisors that may need to work with a variety of other products.
Does the hypervisor type even matter?
As long as the HCI system does what you need it to, the hypervisor software you use doesn't matter. That is most true when choosing an HCI appliance or complete software package, because the hypervisor will most likely be built or customized to work best with its other components.
When choosing a hypervisor for a DIY build of an HCI system, you must be more attentive to the features of the hypervisor you pick. But even here, if you have a choice between hypervisors that all do what you need, the deciding factors become compatibility with other components, ease of use and cost.