KVM vs. OpenVZ: What's the Difference?

When choosing a Virtual Private Server (VPS), one of the most critical decisions involves selecting the right virtualization technology. Among the popular options available today, KVM (Kernel-based Virtual Machine) and OpenVZ (Open Virtuozzo) stand out. But what are the differences between these two technologies, and which one is the best fit for your needs? In this guide, we’ll dive deep into the KVM vs OpenVZ debate to help you make an informed choice.

What is Virtualization?

Virtualization is a technology that allows multiple virtual machines (VMs) to run on a single physical server. Each VM operates independently and behaves like a separate computer with its own resources. This technology is the backbone of cloud computing, enabling efficient resource utilization, scalability, and isolation.

Virtualization in Web Hosting

In web hosting, virtualization allows hosting providers to offer VPS services. By using virtualization technology, providers can create multiple isolated servers on a single physical server. Customers benefit from this setup due to improved security, resource control, and scalability compared to shared hosting.

What is KVM?

KVM (Kernal-based virtual machine) is a virtualization technology that turns Linux into a hypervisor, allowing the host machine to manage multiple, isolated virtual environments. A hypervisor is a program that can run on 1 physical machine to split it up into multiple individual virtual machines. As a full virtualization solution, KVM enables virtual machines to have private virtualized hardware: a CPU, RAM, Disk, etc. This provides a highly secure, scalable environment that can grow and shrink with your needs as a client.

What is OpenVZ?

OpenVZ is a container-based virtualization technology for Linux. Unlike KVM, which provides full virtualization, OpenVZ uses a shared kernel approach. All VMs, or containers, run on the same kernel, which means they must use the same operating system (OS). This makes OpenVZ less flexible than KVM but highly efficient in terms of resource utilization and speed.

KVM vs OpenVZ

KVM vs OpenVZ - Hardware Requirements

KVM requires hardware that supports virtualization, with processors that include virtualization extensions like Intel VT or AMD-V. This can lead to higher hardware costs. In contrast, OpenVZ can run on any x86 processor, regardless of these extensions, making it a more cost-effective option for hardware.

KVM vs OpenVZ – OS Support

KVM supports a wide variety of operating systems since each VM operates independently with its own kernel. You can run Linux, Windows, or any other OS. OpenVZ, however, is limited to Linux due to its shared kernel architecture. This is a critical consideration if OS flexibility is important for your applications.

KVM vs OpenVZ – Kernel Versions

KVM allows each VM to run its own kernel version which can be different from the host kernel. This is beneficial for running applications that are dependent on specific kernel versions. On the other hand, OpenVZ containers must use the host’s kernel, limiting the ability to make kernel modifications or use different versions.

KVM vs OpenVZ – Memory Distribution

KVM provides dedicated memory to each VM, which cannot be exceeded. This fixed allocation ensures that the performance of one VM does not affect another. Conversely, OpenVZ uses a shared memory model, which can lead to better memory utilization but risks one container consuming most of the resources, potentially impacting others on the same server.

KVM vs OpenVZ – Price

The choice between KVM and OpenVZ can also come down to cost. KVM tends to be more expensive due to its resource isolation and hardware requirements. OpenVZ, being more resource-efficient and less demanding in terms of hardware, generally offers a more budget-friendly option. Generally speaking though, the resources on OpenVZ machines have a reputation in the web hosting industry for being more oversold. This means that the web host sells too much of the machine, leading to issues with performance. On KVM services (like Atomic Networks' VPS service), resources tend to be far less oversold.

Which Virtualization Should I Choose?

The decision between KVM and OpenVZ depends largely on your specific needs. If you require full virtualization, OS independence, and high security, KVM is likely the better choice. However, if you prioritize cost-efficiency, resource utilization, and you are comfortable with the limitations regarding OS and kernel flexibility, OpenVZ might be more suitable. Personally, we would recommend choosing a KVM VPS.