Understanding KVM, OpenVZ, and XEN in VPS Virtualization

VPS Virtualization

Have you ever imagined how a VPS works? What is behind a VPS so that it can provide features like a dedicated server?

To answer this question, let’s dissect what a VPS is first.

Technically, a VPS is a virtual machine or Virtual Machine (VM). Where one physical server is divided into several virtual servers.

Well, this sharing process is called VPS virtualization. You do this with the help of a Hypervisor or software that divides physical server resources into several VMs.

So, one physical server can accommodate several VMs at once, with the same resource capacity.

Well, that’s why you can enjoy physical server facilities at relatively affordable prices. Because you don’t need to buy a dedicated server and the cost of operating a VPS is also lower.

VPS performance itself is influenced by what virtualization platform is used. Some of them are KVM, OpenVZ, and XEN.

Each VPS virtualization has different features and advantages. In this article, we will discuss KVM, OpenVZ, and XEN. So, let’s dive deeper into each VPS virtualization.

What is KVM?

KVM or Kernel-Based Virtual Machine is a full hardware virtualization technology developed and running on the Linux operating system. KVM is also suitable for use on x86 CPU types (64 bit).

This type of VPS virtualization has a hypervisor component, such as:

  • memory manager;
  • Process scheduler;
  • I/O stacks;
  • Device drivers;
  • Security settings;
  • Network stacks, etc.

With these devices, the KVM hypervisor can be installed directly on top of a physical (bare-metal) server. So it can be a stable host system because it doesn’t run on other OS.

In terms of security, KVM is superior to the use of containers such as OpenVZ which will be discussed later. Because each Guest OS will use its own kernel.

Advantages of KVM

Generally, KVM is very popular because it is full virtualization and can use various OS. However, there are still several other advantages of KVM that are worth considering as VPS virtualization.


The use of KVM is considered very efficient because the activity of one virtual server (VPS) will not affect other VPS even though it is on the same Hypervisor.

That way, the workload becomes lighter because each VPS can use its own resources.

In Linux processes, KVM is scheduled and managed by the kernel which already includes the core features required by the hypervisor. So, KVM can work more efficiently because there is no need to write all the required components from scratch.

In addition, the Linux kernel has real-time extensions. This extension helps VM-based applications run on lower connections, but with better network priority.

Computing processes that usually take time can take place more quickly. By dividing processes and compressing them into smaller systems. As a result, KVM has lower latency or system delay.

Supported Own RAM and CPU

Still related to the previous point, one of the resources used by each VPS is its own RAM and CPU.

Because it already has its own resources, of course, the system process will be smoother and not interfere with other VPS activities.

KVM memory is also supported by Virtual Memory Management (VMM) and larger memory management for better performance.

Can Use Various OS

You will experience high flexibility with KVM. Because this type of VPS virtualization supports the use of various OS or operating systems.

The operating systems that can be used in KVM include:

  • Ubuntu;
  • Debian;
  • CentOS;
  • Windows;
  • Fedora;
  • Suse.

This is certainly very helpful for your technician in the operational process. Because you can choose which OS best suits your VPS needs.

High Resources

VPS is very suitable as an alternative upgrade from Shared Hosting. Especially if your website is getting bigger and has high traffic.

The bigger the website, the more resources needed. Like, RAM, CPU, Disk Space, Bandwidth, etc. The goal, so that the performance of your website can meet the demand for high activity.

Especially for online stores that require processes or activities such as:

  • Checkout process;
  • Payment validation flow;
  • High level of security;
  • User and consumer databases;
  • Product catalog storage, etc.

All website files that you save such as images, and other data that certainly require storage space to be accessed.

Well, KVM uses various storage systems supported by Linux. For example, local disks and Network-attached Storage (NAS).

NAS or Network-attached Storage is a data storage system specifically intended for backup and share needs. This system can be accessed via the internet.

Another storage that KVM uses is Multipath I/O. The goal, to increase storage by enabling multiple storage connections.

In addition, Multipath I/O also provides failover or automatic switching operations so that storage remains accessible in the event of a hardware error.

Storage KVM is also still being added with shared file system support so that VM images can be shared by multiple hosts.

Migration Without Downtime

Live migration is one of the main features of KVM. You can migrate running VMs between physical hosts, live without any interruption from server services.

This migration is very useful for:

  • Load balancing – Load sharing between hosts;
  • Hardware switch – Safe transfer of the Guest VM to another hardware when the old hardware crashes;
  • Save energy – Host system can be disabled if the Guest VM is not filled, thus saving energy and costs;
  • Geographic migration – Guest VMs can be moved to another location if needed.

So, when a Guest VM wants to move to the Hypervisor, the Guest VM system can continue to run even though it is in the process of moving the server.

Guaranteed Security

KVM uses a combination of Security-enhanced Linux (SELinux) and Secure Virtualization (sVirt) as a security standard.

SELinux sets a security boundary around a Virtual Machine (VM). By distinguishing between the root user and the Guest VM.

Security in the Guest VM is also implemented by limiting access to create, run, and read files (write, executable, read). This is all done so as to prevent errors.

SELinux is also assisted by sVirt to protect hypervisors and VMs from two main threats, namely:

  • Intruder application to access resources;
  • Intruder applications to access or control other VMs and their resources.

What is OpenVZ?

OpenVZ is a virtualization at the OS level or a container-based operating system on the Linux operating system.

This system is a modification of the Linux kernel so that it allows a physical server to run multiple virtual machines or containers.

In its operations, OpenVZ does not rely on virtual technology or VT on the CPU. So the system can run on a number of CPU types, including SPARC, IA-64, PowerPC, and x86, x84.

OpenVZ can only virtualize for Linux-based operating systems, such as Ubuntu, Debian, CentOS, etc. Because it still relies on the Linux kernel, it is not possible to install other operating systems, such as Windows.

However, this operating system can achieve optimal performance, scalability and density because there is a single Linux kernel running on the host.

Well, We as a Cloud VPS service, supports the use of OpenVZ because it has features and advantages that will be explained in the next section.

Advantages of OpenVZ

This Linux-based operating system can be one of the considerations for VPS virtualization, you know. OpenVZ has several advantages that make it worth it to use.

Check out the advantages below.

Save Cost

One of the advantages of OpenVZ is that it is more affordable. This is because OpenVZ is open source, so it can be used with a virtualization license for free.

Easy to use

Another advantage of OpenVZ is its ease of use. You can feel the convenience in memory usage, number of processes, CPU usage, disk usage, etc.

All of that can be changed under conditions that the system is still running and does not interfere with VPS performance. So, you can flexibly customize without restarting containers.

This flexibility is supported by the Checkpointing and Live Migration features. Its function is to migrate containers from one physical server to another without the need to shutdown or restart the container.

How it works, the container will be frozen and all its state will be stored in disk space. After that, the file will be transferred to another computer and can be installed there.

This process only lasts a few seconds, so it doesn’t have a big impact on overall performance.

In addition, the setup and maintenance process for OpenVZ is also easier than KVM. OpenVZ has less overhead, so it can accommodate more VMs than KVM.

Effective Resource Management

In addition to being cost-effective, OpenVZ can also accommodate more Guest VMs.

For example, one VPS server with OPenVZ virtualization has 30 GB of RAM. The server ideally can accommodate a maximum of 30 Guest VM users. So that each user gets 1 GB of RAM.

You can manage this with the Resource Management feature. The goal is to control the amount of resources available to the container. For example, CPU, disk space, memory, etc.

This feature is useful for:

  • Distribute resources effectively to each container;
  • Guaranteeing Quality-of-Service;
  • Provides performance and resource isolation;
  • Protect against interference or error;
  • Collect usage information to monitor system health.

However, this resource sharing is very important, because hosting a Guest VM more than the RAM capacity can potentially cause the system to become slower.


Because it only uses a single kernel, OpenVZ can run very efficiently. Not too many components and settings like KVM.

Due to the simple system structure, OpenVZ has stable performance for managing multiple containers at once.

However, this stability and efficiency is highly dependent on the configuration of the VPS hosting service used.

Powerful Container System

Let’s imagine the containers in OpenVZ are system independent. A container can run independently because it is provided by the kernel virtualization layer in the host OS.

Well, the virtualization layer has the main features implemented in OpenVZ, as follows:

  • Containers have the same system as Linux. For example, using standard scripts, vendor software such as Ubuntu, Fedora, etc., can run without the need for customization with OpenVZ;
  • Can change any configuration file;
  • Can install additional software;
  • Each container does not affect each other;
  • Containers are not tied to a single CPU, but can use all available CPUs.

This container system allows VPS performance to continue to run optimally. Because if there is a problem in one container, it will not affect the other containers.

Network Security

OpenVZ virtualization is designed with container systems and physical networks in mind. This is supported by the network virtualization feature or Network Virtualization, with the following specifications:

  • Each container can have its own IP address;
  • Each container can have multiple IP addresses;
  • Network isolation of each container, the goal is to protect each container from other containers;
  • Can use a firewall, so as to prevent unwanted access;
  • Route table manipulation, for example specifying different source addresses for different destinations. This is for added protection, so that only the assigned IT administrator knows the actual command route.

With all its advantages, OpenVZ is perfect for those of you who need easy management. This virtualization platform is considered very practical and has excellent performance, but is still affordable.

What is XEN?

XEN or XENserver is an open source virtual machine (VM) manager. Developed by the University of Cambridge since 2009.

The goal of XEN is to be able to run hundreds of operating systems using just one computer.

This virtualization is labeled as the fastest and strongest virtualization that can handle many VMs at one time.

This virtual server from Citrix is run based on Linux, it can also help optimize Windows and Linux virtual servers.

The way it works, the XEN server resides on the simple elements of a physical machine. Later it will be allocated to the running VM.

XEN virtualization uses paravirtualization technology. With this technology, XEN is able to provide the following facilities:

  • Multi-server management;
  • Performance alerting and reporting:
  • Live VMs;
  • Live storage migrations.

XEN is also compatible with several Linux operating systems such as Ubuntu, Fedora, OpenSuse.

Advantages of XEN

As a VM manager, XEN is considered to have an advantage that deserves thumbs up. That’s why XEN has been used by more than 50,000 consumers.

It can not be separated from the features that support the performance of XEN. Well, here are some of the advantages that XEN offers in VPS virtualization and its supporting features.

Fast Process

The XEN process in running the VM only takes ten minutes. This is very helpful for IT administrators, because:

  • No need to perform complex management infrastructure configurations;
  • No need to create a dedicated storage network;
  • Can install software and run it as quickly as possible;
  • It’s easy when creating a dedicated network to run the VM on.

Apart from running, XEN is also relatively fast during the VM conversion process because of the XenConvert feature.

It works by converting existing physical and VMs with the help of a VM compatible with XENserver. The benefit, the VM transition will be more practical and easy.

Coupled with the XENMotion Live Migration feature that can be used in all XENserver editions. The point is to move or transfer files from the VM to the server without any downtime on the server.

Additionally, there are privileges to move VMs across resource pools. You also don’t have to worry because all data will be safe, not lost, or other negative effects.

Powerful Server Management

XENserver is a cloud tested platform. This virtualization platform is fully packed with everything needed to create and manage any kind of virtual infrastructure, such as server resources.

The virtual infrastructure can be automated and can be integrated into the management process with the XENCenter Management Console feature.

It functions as a central console control that can run, monitor and manage multiple VMs.

For example, starting, stopping, migrating, creating, copying or backing up VMs is just a few clicks away.

In addition, XENserver will also allocate server management data across resource pools or server resource pools. Well, this will minimize server management failures.

In addition, XEN is also equipped with VM Protection and Recovery features. Its purpose is protection, backup and restore. With this feature, you can create custom policies automatically.

This feature will also collect regularly scheduled VM snapshots. For example, every day, every week, or every month.

The data or snapshots are automatically archived to the remote CIFS, increasing the level of security.

The data can be easily restored as it was before the server was completely wiped. So that server management can be done more optimally.

All these features are also supported by the XenConvert feature which helps the VM in managing data on the server.

Especially VMs that require extra management, this feature can be useful for automation and building powerful management.

Windows OS Supported

Not only supports a variety of Linux operating systems, such as Ubuntu, Fedora, OpenSUSE, etc. XENserver can also be used on Windows OS.

This provides room for IT administrators to use XEN more flexibly.

Support SWAP

The difference between XEN and OpenVZ and KVM is that XENserver supports the use of SWAP.

This technology works when the dedicated memory runs out, SWAP will be activated automatically. If OpenVZ goes down when that happens, then XEN will only experience a slowdown on the server.

But before that happens, XEN has been equipped with the Dynamic Memory feature, which can improve application performance.

It works by sharing unused server memory to other VMs. Thus, server memory space can be more relieved and system processes can run faster.

Without this feature, when the server is full, the VM will encounter problems or “out of memory” errors. So you need to customize the memory allocation for each VM, then reboot.

However, dynamic memory helps you get the unused memory, reducing memory allocation as needed by the VM. This process will automatically run when the server is full.

It is also supported by the IntelliCache feature. This feature can help improve the overall performance of the server. Because it can save storage costs. For example, network volumes, virtual boot times, and traffic.

How it works, IntelliCache uses local storage as a repository for boot images and temporary data. This reduces network volume, virtual boot time and traffic.

KVM, OpenVZ, and XEN: Which is Right for You?

Well, until here you have known three types of virtualization, namely KVM, OpenVZ, and XEN. Complete with features and advantages of each.

All three are often used as VPS virtualization technology. Both Linux-based like KVM and OpenVZ, as well as open source ones like XEN.

All of them can indeed manage multiple VMs at once. However, if you need a virtualization platform that is easy to manage and relatively affordable, then OpenVZ is something you can really consider.

Because it is container based, OpenVZ allows a single kernel to run multiple VMs at once. And that’s what you will get at Our VPS hosting service.

In addition to OpenVZ support, Our Cloud VPS service is equipped with a dedicated IP address, full root access, various control panel options, compatible with more than 50 OS options, 100Mb/S network with 99.9% uptime guarantee, to data loss protection from RAID -10.

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