KVM or VMware: Which Hypervisor is Better?

The range of hypervisors is very diverse. There are numerous solutions from commercial providers, as well as open-source alternatives on the market. Two of the leading products are KVM and VMware vSphere. In the following, we will examine the advantages and disadvantages of both systems and discuss which hypervisor might be the right choice for server virtualisation in different application areas.

What is a Hypervisor?

A hypervisor, also known as a Virtual Machine Monitor (VMM), is software that allows multiple operating systems or servers to run simultaneously on a single hardware. It creates separate virtual environments that operate independently.

There are two different types of hypervisors. Type 1 is installed directly on the hardware and can access the resources directly without an additional layer. Type 2, on the other hand, is installed on an operating system and performs virtualisation from there.

Both KVM and VMware vSphere offer Type 1 hypervisors.

KVM

KVM stands for Kernel-based Virtual Machine and is open-source software. The VMM is part of the Linux kernel and is included by default from version 2.6.20 onwards. KVM itself does not perform any emulations. The QEMU module is required for this purpose. This module allocates the necessary resources such as CPU, RAM, or disk space to the different guest systems. Once QEMU is loaded, the Linux kernel itself takes on the role of a hypervisor.

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Various operating systems can be used as guest systems. The most common ones are Windows, FreeDOS, Solaris, and various BSD derivatives. Paravirtualisation is also possible with KVM.

The software's source code is freely accessible due to the GPL license and can be tailored to the users' individual needs. This allows for great freedom and flexibility.

Advantages of KVM

• Free of charge
• Flexible and customisable software
• Included by default in the Linux kernel

Disadvantages of KVM

• Basic knowledge of Linux required
• No professional support, but community support available

The VMware Hypervisor

VMware is a US-based company founded in 1998 with the aim of providing solutions for Cloud Computing and virtualization software.

With VMware vSphere, the company offers a complete software package that can be used for virtualization. The VMM component is VMware ESXi, a powerful bare-metal hypervisor that is installed directly on the hardware.

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For managing virtual machines, VMware vCenter Server provides an interface. This also allows for activating additional features within the software package.

VMware ESXi is a hypervisor with solid performance. However, due to the additional management software, a virtualization solution using VMware requires more resources than what would be necessary for KVM.

Advantages of VMware

• Easy and flexible control through management via VMware vCenter Server
• Professional support

Disadvantages of VMware

• Costly
• Additional hardware requirements due to the management software

KVM vs VMware: Conclusion

Both KVM and VMware ESXi are powerful hypervisors. Whether it's testing different server variants or running multiple operating systems simultaneously on one hardware, both systems are up to these tasks.

Those with basic Linux knowledge are well catered for with the open-source option. Kernel-based Virtual Machine is particularly suitable for advanced users as they can customise the source code to suit their needs.

On the other hand, with VMware vSphere, users get a complete package that can be expanded with additional features for a fee. It's worth considering that the management software also consumes hardware resources, which could affect the performance of virtual machines.

Also, explore the difference with container virtualisation as in the case of LXC vs KVM.

Our article is based on our own experiences and research as well as information from external sources.

Sources & further links on the topic:
https://www.linux-kvm.org/page/Main_Page (Official Wiki of the KVM community)
https://www.redhat.com/de/topics/virtualization/what-is-KVM (Information from the owner of the KVM developer)
https://www.vmware.com/de.html (Company website of VMware)
https://vmware-forum.de/ (Largest German VMware forum)

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Gerd Altmann on Pixabay