Xen vs. OpenVZ Comparison: Performance, which is a better VPS?

Xen and OpenVZ are two popular, but different virtualization technologies. Each one is a back-end for VPS hosting, and many web hosts, as well as small businesses, are using OpenVZ or Xen to power VPS hosting infrastructure. 

Below is a summary of the key differences that define these common hypervisors:

[table]

,Xen,OpenVZ

Virtualization Type,Bare metal (Hardware virt.),Hosted (OS virt.)

Source,Open-source,Open-source

Target usage,Enterprise,Personal / Private usage

Supported guest OS,Linux / Windows / BSD,Linux

Resource Allocation,Dedicated (Reserved),Shared (As-available)

[/table]

Xen

Xen is a full virtualization solution that virtualizes a host server’s hardware for allocation to different virtual machines. In contrast to other pseudo-virtualization methods, Xen’s virtualization provides complete segmenting and isolation of physical RAM, and other resources. A virtual server running in a Xen instance will have almost exactly the same characteristics as a native installation of the OS on dedicated hardware, with a dedicated kernel, memory, CPU, as well as ‘native’ network and storage devices.

Strengths of Xen:

• Security: VM users cannot ‘escape’ or escalate beyond their containers, which are fully isolated.
• Resource dedication: VM instances use only the resources they are allocated.
• Hardware Virtualization: Operating systems run natively and see native hardware devices
• Versatility: Supports Windows and almost any other OS
• Support: Sponsored by Citrix, Amazon, and others

OpenVZ

OpenVZ is a more lightweight platform that uses host-level (operating system level) virtualization rather than full hardware virtualization. This results in a relatively thin later of virtualization on top of the host server’s operating system, where guest VPS instances will directly share the same core Linux kernel and devices as the host server. This characteristic of OpenVZ, which creates VPS instances that resemble “jailed” instances more than true virtual machines, exposes the system to security and performance risks that are less suited for enterprise or public deployments.

Strengths of OpenVZ:

• Ease of management
• Low overhead
• Seamless resource additions (no VM reboot required)

Performance

Even when considering all aspects of system performance, it is difficult to say whether Xen or OpenVZ instances have better performance. With two containers of equivalent size, in a simple test, OpenVZ may perform better due to its lower overhead (less resources reserved for background operation of the VM). In addition, depending on the host configuration, OpenVZ instances can use resources of the host system beyond what they are assigned. This can result in performance benefits when instances “burst” resources, but may also introduce performance problems when multiple instances are over-using resources simultaneously.

By contrast, Xen instances have dedicated and fixed resource allocations, imposing a relatively fixed limit to the amount of host resources they may consume. Therefore, when we consider a host system with many VPS instances running simultaneously, Xen provides more predictable performance that is guaranteed for each instance. For this reason it is our opinion that Xen virtualization provides better performance in real-world usage.

Interested in trying a VPS?

Check out our VPS hosting service, proudly based on Xen. We host both Linux VPS and Windows VPS instances on our infrastructure in New York, USA and London, UK.