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Operating system virtualization with OpenVZ

Container Service

Hypervisor-based virtualization solutions are all the rage. Many companies use Xen, KVM, or VMware to gradually abstract their hardware landscape from its physical underpinnings. The situation is different if you look at leased servers, however. People who decide to lease a virtual server are not typically given a fully virtualized system based on Xen or ESXi, and definitely not a root server. Instead, they might be given a resource container, which is several magnitudes more efficient for Linux guest systems and also easier to set up and manage. A resource container can be implemented with the use of Linux VServer [1], OpenVZ [2], or Virtuozzo [3].

Benefits

Hypervisor-based virtualization solutions emulate a complete hardware layer for the guest system. Ideally, any operating system including applications can be installed on the guest, which will seem to have total control of the CPU, chipset, and peripherals. If you have state-of-the-art hardware (a CPU with a virtualization extension – VT), the performance is good.

However, hypervisor-based systems do have some disadvantages. Because each guest installs its own operating system, it will perform many tasks in its own context just like the host system does, meaning that some services might run multiple times. This can affect performance because of overlapping – one example of this being cache strategies for the hard disk subsystem. Caching the emulated disks on the guest system is a waste of time because the host system already does this, and emulated hard disks are actually just files on the filesystem.

Parallel Universes

Resource containers use a different principle on the

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