KVM vs OpenVZ

May 27, 2023 | Author: Michael Stromann
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KVM
KVM (for Kernel-based Virtual Machine) is a full virtualization solution for Linux on x86 hardware containing virtualization extensions (Intel VT or AMD-V). It consists of a loadable kernel module, kvm.ko, that provides the core virtualization infrastructure and a processor specific module, kvm-intel.ko or kvm-amd.ko. KVM also requires a modified QEMU although work is underway to get the required changes upstream.
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OpenVZ
OpenVZ is container-based virtualization for Linux. OpenVZ creates multiple secure, isolated Linux containers (otherwise known as VEs or VPSs) on a single physical server enabling better server utilization and ensuring that applications do not conflict. Each container performs and executes exactly like a stand-alone server; a container can be rebooted independently and have root access, users, IP addresses, memory, processes, files, applications, system libraries and configuration files.
KVM (Kernel-based Virtual Machine) and OpenVZ are both virtualization technologies used to create and manage virtual environments, but they have significant differences:

1. Virtualization Approach: KVM is a full virtualization solution that utilizes hardware virtualization extensions (Intel VT or AMD-V) to create isolated virtual machines (VMs). Each VM runs its own kernel and operates as an independent entity. On the other hand, OpenVZ is a container-based virtualization solution that utilizes the host operating system's kernel. It creates lightweight containers, also known as virtual private servers (VPS), which share the same OS kernel but provide isolated environments.

2. Operating System Support: KVM can run a wide range of operating systems, including Linux, Windows, BSD, and more, as it creates complete virtual machines. OpenVZ, however, is limited to Linux-based operating systems since it relies on the host OS kernel for containerization.

3. Resource Management: KVM offers more granular control over resource allocation since each virtual machine is independent and can have dedicated CPU, memory, storage, and network resources. OpenVZ, being a container-based approach, shares the host's resources among the containers. It allows more efficient resource utilization but may have limitations in terms of fine-grained resource allocation.

4. Isolation and Security: KVM provides stronger isolation between virtual machines since each VM operates with its own kernel, file system, and processes. This makes it suitable for scenarios requiring higher security and isolation. OpenVZ, on the other hand, shares the host kernel, which can present some security challenges. While OpenVZ provides isolation between containers, a vulnerability in the shared kernel can potentially impact all containers.

5. Performance: KVM offers near-native performance as it provides full hardware virtualization and runs complete operating systems within each virtual machine. OpenVZ, being a container-based solution, incurs less overhead compared to full virtualization. It allows for higher density and can achieve better performance in certain scenarios by leveraging the shared kernel.

See also: Top 10 Virtualization platforms
Author: Michael Stromann
Michael is an expert in IT Service Management, IT Security and software development. With his extensive experience as a software developer and active involvement in multiple ERP implementation projects, Michael brings a wealth of practical knowledge to his writings. Having previously worked at SAP, he has honed his expertise and gained a deep understanding of software development and implementation processes. Currently, as a freelance developer, Michael continues to contribute to the IT community by sharing his insights through guest articles published on several IT portals. You can contact Michael by email stromann@liventerprise.com