Differences between KVM and OpenVZ virtualization
When it comes to virtualization, clients are often confused in terms of what type of virtualization is better for their purpose. Is it KVM? Or is it OpenVZ? Which one of them does the user need? This blog post has the goal to highlight typical characteristics of the two virtualization approaches and aims at outlining how they differentiate from one another.
First things first, let’s start by looking at KVM.
KVM stands for Kernel-based Virtual Machine. In essence, it is an open source software that is perfect for anyone who wants to exercise full control over the VPS. It represents a full virtualization solution for Linux on x86 hardware. It has virtualization extensions such as Intel VT or AMD-V. The magic that KVM can do is to allow Windows and Linux virtual machines to use the same hardware and still operate side by side without any difficulties posed on the user. The smoothness of work is possible thanks to the private virtualized hardware that each of the virtual machines has. That includes having an own kernel, a network card, disk, graphics adapter and more. Because it has separate virtualized hardware, the virtual server will be able to perform on its own, without being interfered in any way by the other virtual server.
Advantages of KVM
- Full virtualization, so it acts as a dedicated/physical server
- Running multiple virtual machines
- Linux, BSD and Windows support
- Dedicated resources (except for the CPU / NIC since they are shared)
- Usage of OS templates
- Offering users the option to install the OS manually
- Individual kernel and separate modules
- Separate virtual disk, graphics adapter, network card
- Flexible migration capabilities
Disadvantages of KVM
Because KVM VPS has its own kernel/OS, respectively it uses extra system recourses (memory).
OpenVZ, on the other hand, is a container-based virtualization for Linux, where an operating system (OS) shares resources between isolated parts (containers). That makes it a great choice for customers with VPSes that have low amount of memory. To present it differently, virtualization at this level means that all of the basic components are placed on the machine and are used by all the guests. However, despite the fact that the containers share the same OS, each container functions like a standalone server. This makes it possible for the container to be rebooted independently. Moreover, it enables it to have users, IP addresses, memory, processes, applications, root access, and configuration files.
Advantages of OpenVZ
- Container-based virtualization
- Shared kernel with the host
- Less memory or disc recourses usage, since the OS shares the kernel with the OS
- Better performance compared to KVM, since there is no additional virtualization layer between the host and your VPS
Disadvantages of OpenVZ
- Using OS templates only, but offering no option to install your Operating System manually
- Not all kernel modules are available
In conclusion, in case you are wondering what virtualization to choose, first ask yourself the question what precisely will work on your server.