A comparison between OpenVZ and KVM.
What is a KVM Server?
A KVM Server (virtual server) is a virtualization solution that uses the infrastructure of the Linux kernel for complete virtualization. With such a kernel-based virtual machine, the complete virtualization of any operating system is possible. In contrast to OpenVZ VPS, the entire operating system is virtualized, including its own kernel and individual network settings. Even the installation of non-Linux systems is possible without any problems. At first, KVM only seemed to represent a niche solution, but with version 2.6.20, following direct implementation in the Linux kernel, it rose to become the de facto standard for full virtualization in the Linux area. The leading distributors Suse Linux, Red Hat, CentOS and Ubuntu have been using KVM as the preferred virtualization solution over its predecessor XEN for some time now.
How much does a KVM Server cost?
The prices for KVM Servers are based on the traffic, RAM and possible storage space provided. Very affordable offers with a few gigabytes of storage space and less than one gigabyte of RAM are available at low monthly prices. Significantly more powerful KVM Servers are available at higher prices, whereby the upper limits are open. Here it is important to check your own needs carefully. Setting up a KVM Server is usually free of charge, some providers charge low fees. In the case of very cheap offers, the selection of the available operating systems can sometimes be limited.
Who offers KVM Servers?
Most known providers of network services now offer KVM Servers. In addition to premium providers, it is often worth taking a look at smaller providers who have affordable entry-level offers. When choosing a provider, your own needs and the reliability of the respective provider, together with the price, should play a decisive role.
What are the advantages and disadvantages of a KVM server?
Compared to OpenVZ, KVM Servers offer some advantages that result from full virtualization:
- Installation of own images possible
- Installation and configuration of your own kernel
- Firewall over iptables
- Snapshots can be created during operation
- The size of the SWAP memory can be freely determined
- Top security and speed.
Disadvantage: KVM is more difficult to set up and manage than OpenVZ.
What alternatives to a KVM Server are there?
In the case of virtualization via a kernel-based virtual machine, in principle all type 2 hypervisors can be considered. These are based on a normal operating system and use its drivers. Well-known alternatives to KVM are for example Microsoft Virtual Server, OpenVZ or Linux Server.
What is OpenVZ and how does it work?
OpenVZ is software developed from the commercial Virtuozzo project for the virtualization of operating systems. It uses a specially adapted Linux kernel that administrates the distribution of resources between the running subsystems. In contrast to commercial solutions like VMWare, it uses the open source license GPL V2. All operating systems run at OpenVZ in individual, strictly isolated containers. Each container is assigned a fixed storage capacity as a virtual hard disk. The additional environment, such as the available RAM memory or the proportion of CPU usage, can also be defined individually for each container. One of the special advantages of OpenVZ is that the assignment can be changed at any time. It is not necessary to shut down the running system. Access from one container to another is not possible within the software. OpenVZ servers therefore offer a high level of security. From the user’s point of view, an OpenVZ server differs from a physical server in only a few details. One restriction is that you cannot install your own kernels.
What are the costs of an OpenVZ server?
The real costs depend heavily on the provider. They are calculated according to the size of the permanently allocated and variable RAM memory, the capacity of the hard drive and, under certain circumstances, the network traffic. Since OpenVZ is open source, unlike commercial solutions, there are no license fees for the provider. OpenVZ servers are therefore usually cheaper than other virtual servers with comparable equipment. Some providers charge additional setup costs when installing the OpenVZ. An upgrade to higher capacities, for example for more computing performance or a larger storage space, is usually possible without any problems and at no additional cost.
Which web hosting companies offer OpenVZ servers?
It is not always clear to the customer which virtualization solution a provider is using for its systems. In most cases, however, it does not play a decisive role, as it provides a complete operating system regardless of the software used. Many web hosts use OpenVZ in parallel to other programs such as Xen or VMWare. If the customer expressly wishes to operate an OpenVZ server, he can fall back on the correspondingly marked offers. Otherwise, a simple short query to the provider clarifies whether they offer OpenVZ or only use other virtualizations. However, OpenVZ holds a relatively high market share because of its efficiency, stability, and security. Many virtual Linux servers are therefore controlled via OpenVZ.
What are the advantages and disadvantages of OpenVZ?
- Low costs thanks to open source software
- Server properties can be changed during operation
- Different Linux distributions are possible
- Full operating system with root access
- Unlimited software installation possible
- Safe environment through isolated containers
- Relatively easy to set up and handle
- All containers use the same kernel
- OpenVZ only supports Linux servers
- Kernel cannot be updated or modified
- Graphic systems are not always supported
What alternatives to OpenVZ are there?
Because of its simple configuration, its high performance and other advantages, OpenVZ has a high market share in virtual Linux servers. In recent years, many larger providers have increasingly been using KVM VPS to counter problems such as the lack of support for their own kernel.
Difference between KVM and OpenVZ.
OpenVZ is not a “real” virtualization solution in which an entire server is virtualized. OpenVZ is also known as the Linux container. The virtual server uses large parts of the Linux host operating system – including its kernel – but provides separate environments as “virtual servers” for the individual users.
This also includes a restriction: the hardware is accessed directly – without a virtualization layer. This is especially true for the main memory. All guests share the RAM of the host system – but this is not reserved when the virtual guest server is started. In this way, 50 hosts with 1 GB Ram each can be operated on a server with 32 GB Ram. As long as the RAM is not used, everything is fine – but if all guest systems want to use the RAM made available to you at the same time, this has a significant impact on performance. It will make the system slower.
KVM solution, for even more performance.
Normal Servers are provided with Linux Servers (container virtualization). KVM, on the other hand, is 100% full virtualization. This means that with KVM you really have full access to all hardware-related functions. Your own kernel, network settings, mount your own ISOs, VNC console and your own CPU cores that are exclusively available to you. With KVM you can even install non-Linux operating systems. With KVM, you will further reduce the differences between a virtual and a dedicated server. KVM servers offer the possibility of importing and configuring your own kernels. The booked hardware resources are also assigned to the virtual instance even harder, which enables a significantly more stable operation.
KVM or OpenVZ – a conclusion.
I hope that above comparison between OpenVZ and KVM, makes it easier to you to decide which of the two techniques is best for you. To conclude this article we can say in general that more advanced users will probably opt for the KVM solution while, in most cases, less experienced users will prefer to use the OpenVZ system. As you have been able to read both systems are based on excellent virtualization techniques and both are probably equally popular among VPS users. Good luck with your VPS!