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OpenVZ is an operating system-level virtualization technology based on the Linux kernel and operating system. OpenVZ allows a physical server to run multiple isolated operating system instances, known as containers, Virtual Private Servers (VPSs), or Virtual Environments (VEs). Compared to VEs such as VMware and paravirtualization technologies like Xen, OpenVZ is limited in that it requires both the host and guest OS to be Linux. However, OpenVZ claims a performance advantage; according to its website, there is only a 1–3% performance penalty for OpenVZ as compared to using a standalone server.

XEN PV (Paravirtualization) is an efficient and lightweight virtualization technique introduced by Xen, later adopted also by other virtualization solutions. Paravirtualization doesn't require virtualization extensions from the host CPU. However paravirtualized guests require a special kernel that is ported to run natively on Xen, so the guests are aware of the hypervisor and can run efficiently without emulation or virtual emulated hardware.

Xen HVM (Hardware Virtual Machine) guests require CPU virtualization extensions from the host CPU (Intel VT, AMD-V). Xen uses a modified version of Qemu to emulate full PC hardware, including BIOS, IDE disk controller, VGA graphic adapter, USB controller, network adapter etc for HVM guests. CPU virtualization extensions are used to boost performance of the emulation. Fully virtualized guests don't require a special kernel, i.e. Windows operating systems can be used as a Xen HVM guest. Fully virtualized guests are usually slower than paravirtualized guests, because of the required emulation.