An anonymous reader writes:
Xen is a hypervisor level virtualization technology that allows multiple operating systems to be run with and with out para-virtualization. OpenVZ is an operating system level virtualization technology that allows creation of virtual environments similar to virtual machines that are more powerful than traditional jails. Though OpenVZ does not allow running multiple operating systems, the gain in performance due to running virtual containers in a single operating system kernel is very appealing. Xen trades off performance for much better isolation and security. How big is the trade-off ? A performance evaluation study done by researchers at the University of Michigan and HP labs provides insight into the cause of overheads (primarily L2 cache misses). From the tech report,
... We compare both technologies with a base system in terms of application performance, resource consumption, scalability, low-level system metrics like
cache misses and virtualization-specific metrics like Domain-0 consumption in Xen. Our experiments indicate that the average response time can increase by over 400% in Xen and only a modest 100% in OpenVZ as the number of application instances grows from one to four. This large discrepancy is caused by the higher virtualization overhead in Xen, which is likely due to higher L2 cache misses and misses per instruction. A similar trend is observed in CPU consumptions of virtual containers. We present an overhead analysis with kernel-symbol-specific information generated by Oprofile
