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04/03/2025

12. Server Virtualization Software Comparison

It has been about 25 years since server virtualization software first appeared on x86 systems. Initially, VMware had an overwhelming share of the market, but now Linux KVM is also widely used. Linux KVM-based services are especially popular among virtual machine services provided by public cloud vendors (such as Amazon EC2 and OCI Compute).

In this column, we have covered Oracle Linux KVM as server virtualization software several times. We will look back on the history of server virtualization software and explain the current options and points to consider when selecting one.

The emergence and evolution of server virtualization software

The first server virtualization software for x86 systems, VMware Workstation, was released in 1999. In 2001, VMware ESX Server, the initial version of the current VMware vSphere ESXi, was released.

Even before the advent of VMware, virtualization technology existed for general-purpose computers and high-end UNIX servers to divide a single server into multiple servers, but it was a shock when it became available on inexpensive x86 systems.

Since then, server virtualization has become commonplace due to dramatic improvements in hardware performance and the evolution of server virtualization software. Here, we will briefly touch on the improvements in hardware performance and look back on the history of server virtualization software.

Hardware performance improvements

The biggest influence on the spread of server virtualization has been the improvement in hardware performance. Currently, even low-end servers are equipped with CPUs with around four cores, and it is not uncommon to see CPUs with more than 50 cores. Server virtualization has become an indispensable technology for efficiently using these servers.

In addition, hardware performance has improved dramatically between 20 years ago and now.

  • Multi-core and many-core CPUs
  • Increased number of CPU threads with Hyper-Threading and Simultaneous Multi Threading (SMT)
  • CPU virtualization support technologies such as Intel VT and AMD-V (AMD SVM)
  • The spread of large-capacity memory in the hundreds of gigabytes to terabytes range
  • Accelerating disk access with SSD/NVMe

Evolution of server virtualization software

There are many server virtualization software programs available to date. Here we will introduce the major software programs that have been released so far.

Since the appearance of VMware
VMware ESX (now VMware ESXi), efficient virtualization using hypervisors has become possible. In addition, it now has many functions, such as live migration using vMotion and the appearance of the powerful management tool, vCenter Server.

If you look at the VMware website, you can see that there are many editions of VMware vSphere alone, with a wide range of functions. In addition, many related products such as vSAN and NSX have been released.

Xen
Xen was the first hypervisor to appear in Linux. The first version was released in 2003, and since then, Citrix Systems, Oracle and other companies have released Xen-based hypervisors.

The product released by Oracle at this time was Oracle VM Server for x86. Oracle VM Server enabled hard partitioning, something that had not previously been allowed in virtualization environments such as VMware.

Oracle VM Server is still in use, but Premier Support has already ended, and it has been announced that Extended Support will end in June 2024. The successor product is Oracle Linux KVM, which will be described later.

Linux KVM
KVM (Kernel-based Virtual Machine) was merged into the Linux mainline kernel in 2007. Initially, it was inferior because Xen was superior (Amazon EC2 was also initially based on Xen). However, since it was integrated into the mainline kernel, it gradually gained the upper hand, and now KVM is the mainstream Linux hypervisor.

Additionally, many public clouds, such as Amazon Web Services, Oracle Cloud Infrastructure, and Google Cloud, use systems based on Linux KVM.

KVM is included in the Linux kernel and is therefore available in most currently released Linux distributions.

Oracle Linux is one of them, and there is no product called Oracle Linux KVM. You can use KVM with regular Oracle Linux. In addition, by combining it with Oracle Linux Virtualization Manager released in 2019, you can not only achieve integrated management, but also achieve hard partitioning similar to Oracle VM Server.

An example of a product specialized for virtualization is Red Hat Virtualization (formerly known as Red Hat Enterprise Virtualization), released by Red Hat in 2009.
The product was optimized for virtual environments and bundled with management tools, but it has been announced that the maintenance support period will end in 2022, and the longest extended life phase support will end in August 2026.

Red Hat Virtualization is currently incorporated into the container platform Red Hat OpenShift and exists as a feature called Red Hat OpenShift Virtualization.

Microsoft Hyper-V
Hyper-V was introduced in 2008 as one of the features of Windows Server. Initially, it suffered from insufficient performance and a small number of supported guest operating systems, but it has now been adopted as the foundation for Azure. Some editions of Windows 8 and later also have client Hyper-V, but this article focuses on Windows Server Hyper-V.

Other options

So far we have introduced the major hypervisors, but in recent years other server virtualization technologies have also been used. We will introduce a few of them here. However, because they are positioned differently from the hypervisors we have explained so far, they will not be included in the comparison in the next chapter.

This product is classified as Nutanix
Hyperconverged Infrastructure (HCI). It is a product that combines the functions required for server virtualization into one, and includes all components of servers, storage, networks, and software. It is pre-set up, so it can be built in a short time, and it is all provided by a single vendor, so it reduces complexity and operational costs.

As a hypervisor, the Linux KVM-based Nutanix AVH can be used by default, and external hypervisors such as ESXi can also be used.

The disadvantages are that it is difficult to build with the desired number of CPU cores because the server configuration is limited, and there are limitations on I/O performance because it is software-based storage. However, Nutanix can also use external storage.

OpenStack
OpenStack is software for building cloud computing environments. It is mainly used in private cloud environments and includes virtual machines, storage, networks, management tools, etc. It supports hypervisors such as KVM, ESXi, and Hyper-V.

Initially, it was expected to be a cheap virtual environment, but due to its complex structure, difficulty in building and operating, short release cycle of six months, and limited maintenance period, it is now used as the infrastructure of some technology companies and public cloud vendors.

OpenStack is also released as a distribution, such as the Red Hat OpenStack Platform.

Table 01: OpenStack and public cloud component compatibility table

OpenStackAWSOCI
ComputeNovaEC2Compute
networkNeutronVPCVCN
Block StorageCinderEBSBlock Volume
Object StorageSwiftS3Object Storage
Operational Management ToolsHorizonManagement ConsoleOCI Console

Containers
Starting with Docker, which appeared in 2013, Kubernetes became the standard as a container infrastructure orchestrator around 2018. Server virtualization using containers has higher consolidation power, is faster, and is lighter than hypervisors. It is also compatible with DevOps, so it is welcomed by advanced application engineers.

However, its use in on-premise production environments is limited for the following reasons, especially when there are existing applications.

  1. The Kubernetes release cycle is fast (one version is supported for nine months), and the Kubernetes itself and the ecosystem are evolving at a ferocious pace, making it difficult to keep up.
  2. Troubleshooting is more difficult than with virtual machines
  3. Existing applications need to be modified because the mechanism is different from that of virtual machines.

Issue 1 can be mitigated by using managed services in the public cloud, but this is not available on-premise.

Server virtualization software comparison

So far, we have introduced several server virtualization methods. This time, we will compare the following three products as on-premise hypervisors.

  • VMware vSphere
  • Microsoft Hyper-V
  • Oracle Linux KVM

In fact, 10 years ago, VMware was overwhelmingly superior. However, since then, the spread of public clouds and the use of Linux KVM by many public cloud vendors have improved significantly, and now there is no difference in basic functions such as functionality, performance, and stability (Azure uses Hyper-V). Some survey results even show that KVM is superior in terms of scalability.

For example, the AWS Nitro System, which forms the basis of Amazon EC2, consists of hardware using a dedicated SoC (System on a Chip) and a KVM-based hypervisor.

In this software comparison, we will look back and compare the overviews as well as the cost and operational aspects where differences appear.

Overview Comparison

The following table shows the basic overview and main features of each hypervisor. There are more detailed comparison tables out there, but there is not much difference between them, so we will leave it at this level. Please just look at this table to get an overview of each one.

Table 02: Hypervisor Comparison (Basics)

*1: This only indicates that the hypervisor has the function, but it may not work depending on the host and guest settings.

Cost Comparison

The biggest difference is the cost of licenses and support. VMware and Hyper-V have complicated pricing and some parts are not publicly available, so I won’t give you specific prices, but if you’ve ever gotten a quote for each, you’ll know that Oracle Linux KVM is overwhelmingly cheaper. Also, if you’re using Oracle products, it’s certified as hard partitioning, so you can significantly reduce your Oracle license costs.

Table 03: Hypervisor Comparison (Cost)

Comparison of operational aspects

Contrary to the cost aspect, Oracle Linux KVM is inferior in terms of operation. Even if your favorite vendor’s server is not officially supported, you can solve the support issue by using Oracle’s Oracle x86 Server. The problem is the lack of third-party tools such as backups and engineers with the know-how.

Table 04: Comparison of Hypervisors (Operation)

summary

Now that the differences in basic functions, performance, and stability have narrowed, the important points to compare are “cost” and “operation.” If you have a large budget and want to operate safely, VMware is a strong choice. Also, if you use a lot of Windows Server, Hyper-V should have a high affinity.

Oracle Linux KVM is attractive for those who are concerned about cost. It is license-free and support is inexpensive. Especially when using Oracle products, the price difference with other companies becomes more noticeable because you can use hard partitioning. The remaining concern is the operational aspect. Whether this is solved by training in-house engineers or by a good partner may be decided by each company’s policy and encounter.

For reference, Oracle has published a comparison document between KVM and VMware vSphere, which I would like to introduce.