Whereas VMware virtualizes and emulates the hardware layer, [link|http://www.infoworld.com/article/06/04/21/77439_17TCvirtu_1.html|Virtuozzo] runs with the native OS on the host server and creates VPSes (virtual private servers), by generating chroot jails for the host. It then tightly controls the network and kernel layers to deliver packets correctly and to handle disk, memory, and CPU quotas.

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A likely scenario for production use of Virtuozzo is on quite high-end hardware, so I did my tests on an HP ProLiant DL585 with four dual-core Opteron 852 2.4GHz CPUs, 16GB of RAM, and 100GB of local RAID5 storage.

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I then created 100 VPSes on the DL585. First selecting a VPS template for FC4, and then specifying that I wanted to create two VPSes with the base FC4 distribution, all the development tools, and php4, I was able to determine the CPU, disk, network, and RAM quotas for these servers, their network addresses, and root passwords.

When I was finished with the wizard, it took approximately two minutes for each VPS to get up and running. Next, I created 16 CentOS 4 VPSes in the same fashion, followed by 32 Red Hat AS 4 VPSes. All told, I easily reached the 100 VPS goal. In fact, by the end of my testing, the four-way DL585 was running more than 300 VPSes. Impressive.

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In terms of performance, I found Virtuozzo introduced very little overhead. In a pure static Web-serving test, I reached about 97 percent of the host systems\ufffd throughput scores when running the same test against 100 VPSes simultaneously.