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Head to head comparison KVM vs Xen

If we talk about the concept of virtualization that has changed a lot in any developer's life, hypervisors are the new technology that has been an addition to virtualization. If you want to merge the server space or in case you want to run several independent machines on a particular host then you can use a hypervisor. With the help of the hypervisor, you can control and manage your data centrally along with the implementation of virtualization.

Head to head comparison KVM vs Xen

As with time, the usage of hypervisors is expanding day-by-day that is resulting in the creation of centralized storage ponds to be used as storage hypervisors. Not only the storage, but it also plays with the network in such a way that the data can be effectively formed, managed, manipulated, or even destroyed without affecting the actual data and the network devices. In this way, you can efficiently broaden the network virtualization.

In this article, we are mainly focused on:

  • Why we need virtualization
  • Learn about two hypervisors KVM and Xen
  • Their pros and cons
  • Their differences

These KVM and Xen are the type 1 of hypervisors that are available in the market.

Why do we need virtualization?

Virtualization is important from various perspectives, it will help you in saving time, money, and effort. You can even manage and optimize your resources efficiently. Also, you will get to access the remote servers securely, resulting in enhanced productivity. It will help you to prevent the loss of data over the network.

The VM acts as an interface between the hardware and the operating system which is basically used to provide the required access that an application should have with the underlying processor and other related hardware devices. 

There are some types of virtualization that you can leverage within your system.

  • Server virtualization - this type of virtualization helps in running various operating systems on a single physical server which are highly efficient VMs. They are beneficial for reducing operational costs, enhancing server availability, helps in eliminating the complexity of the server, faster deployment of workloads, and many more.
  • Network virtualization - it allows the applications to run on a virtual network as efficiently as they are running on the physical server, enhancing operational capacity. 
  • Desktop virtualization - it deploys the desktop as a managed service that helps the organizations for responding effectively as per the changing workload demands. 

What is KVM?

KVM or you can recognize it as a Kernel-based Virtual machine which is a virtualization infrastructure, especially for the Linux kernel. You can use this hypervisor with the Linux operating system along with the great support for Windows, BSD, and Solaris but only as a guest.

You can run KVM on x86 and x86-64 systems that come with the amazing support for the Virtualization extensions. It was designed as an open-source option, consisting of a wide range of kernel modules. Such modules help in providing the virtualization infrastructure core along with the processor-specific module. 

It initially hit the market in 2006 and emerged with the mainline Linux kernel versions after that. There was no requirement for any special arrangement for this open-source virtual solution. For operating the virtual machines, hypervisors require some of the components at the OS level like input/output stack, memory management, process scheduler, security, and many more.

These components are included within KVM as it is a part of the Linux kernel. You can convert Linux into the native hypervisor using KVM. This lets you run every machine as a regular process and get dedicated hardware like memory, disks, CPUs, and others.

As KVM is integrated with Linux, so KVM has all the Linux components. KVM is preferred due to its great hardware support, security storage, performance, flexibility, and many other features. 

Pros of Using KVM

Today, many users prefer KVM as one of the best options available for virtualization in the market. We have mentioned a few benefits of using KVM.

  • It offers you excellent security as it has a base of Linux and comes with the benefit of SE Linux advanced security system. It helps in ensuring the virtual machine’s security at a high level. It has been praised for meeting the high-security standards as per the government. 
  • It is available for every user. It comes with an open environment, allowing users to use and customize it as per their business requirements.

Cons of Using KVM

Below are some cons of using the KVM.

  • Apart from being amazing in all aspects, it has a limitation of complex setup processes. It is considered to be more complex when compared to other alternatives.
  • It has limited support of processors due to the fact that any system will not be able to use all the resources.
  • It lacks the built-in CPU virtualization support, impacting its performance to some extent.
Feel free to check out the comparison between KVM and Vmware here.

What is Xen?

This project started when there was no other alternative available for virtualization. Due to some limitations of Jail/container leads to the introduction of Xen in 2004. It was one of the type 1 hypervisors meaning there is a single layer above the bare metal. It acts like a stripped-down OS, using the “pass-through” function for connecting to PCI devices.

With Xen, you will be able to make formation, implementation, and management of several VMs with a single host. In 2007, XenSource launched Xen. Due to its type 1 feature, you can use it directly on the computer’s hardware without the need for a host OS. it comes with support for Windows and Linux. Apart from this, it has support for IA-32, ARM, and x86 processors. You can even customize it due to its unique structure. 

XenServer is considered to be the first choice for hyper-scale industrial clouds like Alibaba, Amazon and Oracle Cloud and IBM Softlayer as it offers you a flexible structure. It is based on an approach for detecting and enhancing protection, making Xen a secured hypervisor option. Xen’s architecture comes with an advanced security facility, making it a commonly adopted choice in security-related environments.

Pros of using Xen

  • As it is available for free, it is well-suited for small organizations.
  • As it is available as an open-source, you may not face vendor lockdown issues.
  • It allows the live migration of virtual machines, keeping your system running irrespective of any hardware changes in the background.
  • Its GUI has a great learning curve, making it easier to understand.
  • It comes with the snapshot feature, ensuring security against malware and risky upgrades.
  • It helps inefficient management of resources.
  • It helps in moving the virtual server from one physical server to another without any risk.
  • It has a small environment, allowing easy configurations.
  • It has an easy console for making upgrades to the hypervisor pool.
  • It helps in managing the failure really well as it has copied the pool database on each host.

Cons of using Xen

Below are some limitations while you use Xen hypervisor.

  • Its free version has some limitations so you need to go for a paid version to leverage all of its benefits. It is more suitable for large companies.
  • It lacks the support for USB devices.
  • It comes with less technical support and you might not find much on Google as it is barely used.
  • The virtual networks are less stable.
  • The upgrade process it supports is buggy and complex.
  • It is a complex task to add additional storage to the host.
  • You need to reboot the products more frequently due to the hung up of the DOM kernel.
  • Whenever you delete the virtual machine, it will leave the orphaned vdisks.

The difference between KVM and Xen

We have mentioned a few differences between the KVM and Xen virtualization.

  • KVM is considered to be a lightweight hypervisor module that is based on the Linux kernel. This kind of virtualization requires hardware support like CPU with VT function. KVM allows the running of the CPU that comes with the virtualization support. While on the other hand, Xen acts as a virtualization solution that comes under Linux. You can only implement Xen that is based on kernel supporting Xen functions. The kernel that comes with the support for the Xen is known as Domain0. 
  • The kernel module of KVM is known as kvm.ko which realizes the CPU’s virtualization and Linux memory. It helps in allocating VCPU and memory as a process of Linux. While Xen can be effectively run on the hardware of a computer, replacing the OS. you will be able to run several guest OS simultaneously on the computer's hardware.
  • KVM has been introduced into the kernel of Linux by the Linux core organization while Xen acts as an external hypervisor program that helps in controlling the VMs and allocating the resources to several clients. 
  • If we want to update the Xen version, then we need to recompile the complete kernel while it is not required in KVM up-gradation and does not require any kernel modification. 

KVM and Xen difference comparison table

Comparison item

Xen

KVM

Released 

2003

2007

Supporting enterprise

Citrix, Novell, Oracle, Ret Hat (RHEL5) and Virtual Iron

Redhat, Ubuntu, etc.

Supporting virtualization technology

Full virtualization, paravirtualization

Full virtualization

Supporting structure

x86, IA64 and ARM from AMD, Fujitsu, IBM, Sun and other companies, as well as x86/64 CPU vendors and Intel CPU embedded support

CPU that supports virtualization

Supporting operating system

UNIX, Linux and Microsoft Windows

UNIX, Linux and Microsoft Windows

Live migration

stand by

Support (not previously supported)

Kernel support

Need to patch the kernel

Built-in the kernel

Conclusion 

Virtualization has brought a huge change in the IT world and has made deployment easier at every platform. With the introduction of KVM and Xen two hypervisors written in C language. Both of them show some differences that we have mentioned in this article. You can choose any of the hypervisors as per your choice and business requirement. 

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Nisal N

Computers has always fascinated me since I was a kid and here we are. I love travelling for 2 reasons: the first one to see a new part of the world and second (the most important one) to experience the rich culture hidden among the country and people. I'm pretty good at cooking but very poor when it comes to baking.

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