All About Hypervisors — Part I: Differences Between vSphere, KVM, Hyper-V and XenServer

Published On: 18th March 2021//3.9 min read//Tags: , , , , , //

StorMagic has a long history of supporting compatibility with many different server vendors and hypervisors, for our high availability storage solution, SvSAN. Hypervisors provide the foundation for virtualization platforms and there are several options to pick from, from traditional vendors to open source alternatives. VMware is a popular choice for virtualization, along with the ESXi hypervisor and vSphere virtualization platform. Yet, the popularity of Linux has placed greater emphasis on Kernel-based Virtual Machine (KVM) as its open-source option.

What is a Hypervisor?

A hypervisor, or virtual machine monitor (VMM), is software that manages virtual machines (VMs) and translates requests between physical and virtual resources. Hypervisors allow a single piece of hardware (i.e. a host)to support multiple VMs (i.e. guests), by virtually sharing its resources (i.e. memory, storage, and processing). The hypervisor doesn’t perform any of the actual CPU execution, it simply manages the resourcing and scheduling.

Key Benefits of a Hypervisor

Leveraging a hypervisor to host multiple virtual machines is beneficial for a number of important reasons, including:

  • Easier to provision resources for dynamic workloads
  • Enables users to create virtual machines instantly
  • Improves efficiency by only requiring one physical server versus multiple
  • Allows organizations to be  hardware agnostic, since the hypervisor separates the operating system from the underlying hardware
  • Increases flexibility by allowing VMs to be portable and IT team to shift workloads across multiple servers
  • Increases security since virtual machines are isolated from each other
  • Enables users to run multiple operating systems on the same hardware

VMware vSphere platform

VMware offers the ESXi hypervisor and vSphere virtualization platform. VMware ESXi is a bare-metal hypervisor that installs directly onto a physical server and helps organizations consolidate their hardware. VMware’s virtualization technologies enable the creation and provisioning of virtual machines (VMs), so organizations can modernize their infrastructure to deliver and manage new and legacy applications.

Choosing VMware vSphere requires users to manage their VMs using VMware’s control stack; there are several license entitlements levels available.

KVM hypervisor

KVM is an open-source virtualization technology. It changes the Linux kernel into a hypervisor that can be used for virtualization, and is an alternative to proprietary virtualization technologies, such as VMware.

Migrating to a KVM-based virtualization platform enables the ability to inspect, modify, and enhance the source code behind one’s hypervisor. Having access to the source code opens the door to innovation, allowing users to virtualize traditional workloads and applications and build a foundation for cloud-native and container-based workloads. It’s easy to use and deploy because KVM is built into the Linux kernel.

Hyper-V hypervisor

Hyper-V is a built-in component of all modern versions of Windows. Therefore,  users don’t need to purchase any additional software from Microsoft to utilize Hyper-V. If you own a modern Microsoft operating system, you already own Hyper-V.

Hyper-V runs directly on the host computer hardware. For Windows users, a clear advantage is the close connection to the operating system. This can also mean a more cost-effective solution because Hyper-V is often included for free with Windows, and it is relatively simple. Even beginners can benefit from virtualization via Hyper-V.

Although Hyper-V works very well with Windows, the software reaches limitations with other operating systems. Hyper-V is not designed to run on other systems, and the possible guest systems are very limited. Apart from Windows, only a few selected Linux distributions can run in a virtual machine. For example, if you wanted to use macOS as a guest system, you’d have to use an additional product. In addition, running multiple Linux systems at once leads to a significant drop-off in performance.

Citrix XenServer

Based on Xen Project Hypervisor, XenServer is an open-sourced bare-metal server virtualization platform. It consists of enterprise-grade features that easily handle workloads, combined OS, and networking configurations. XenServer is the most highly optimized hypervisor platform for Citrix Virtual Apps and Desktops workloads.

Choosing between XenServer versus other hypervisors generally depends on the size and type of business, and budget. VMware’s vSphere, for example, has a much higher price tag than XenServer overall, and vSphere licenses do not come with maintenance. Citrix XenServer, although not free, is less expensive than vSphere, and is an excellent solution when it comes to integrating other Citrix platforms like Virtual Apps and Desktop workloads.

If cost is a concern, a recent open-source project called XCP-ng provides access to all of the same XenServer features for free.

There are several different factors to consider, when selecting a hypervisor. Stay tuned for part two of this blog series, where we’ll discuss the criteria for choosing the right hypervisor, and the differences between Type-1 and Type-2 hypervisors.

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