Red Hat claims it can run five virtual machines (VMs) for every three that VMware's ESX runs in the same server hardware. Qumranet technology also enables it to run more Windows virtual desktops than VMware, too.
At a journalists' roundtable in London this week, Benny Schnaider, Qumranet CEO, said his - now Red Hat's - company's KVM (kernel-based virtualisation machine) hypervisor runs 52 VMs in a physical server, in which ESX can host a maximum of 35 VMs. Citrix Xenserver is worse: it can only host 30.
There are two reasons why KVM is better than ESX, according to Schneider.
First, KVM is newer code: when it started being designed four years ago Intel and AMD were already extending their processor instruction sets to add virtualization-supporting instructions. Early hypervisors like ESX had to cope with the previous generation of CPU chips, which had no virtualisation support, and so were larger and made less efficient use of server resources.
In other words, VMware is held up by legacy code baggage, and Qumranet is not, or so Red Hat says.
Second, Windows needs lots of memory and is a bulky VM in RAM terms, according to Schneider. He hinted that KVM can reduce this Windows VM memory burden, freeing up RAM for other VMs.
Qumranet also provides Red Hat VDI (virtual desktop infrastructure) technology, which supports more remote desktops and gives the users a better experience because of its SPICE rendering technology. It compresses the desktop data stream better and enables a Linux server to be a better Windows VDI host than a VMware or Citrix Xenserver server. Red Hat CTO Brian Stevens acknowledged that it's a little odd that Red Hat's desktop strategy is now focused on the virtualized Windows desktop.
Paul Cormier, Red Hat's SVP for engineering, said Red Hat's strategy is to enable customers to virtualise everywhere if they so choose, from the Android cell phone to the desktop. He probably doesn't mean we'll be able to run Vista on Android, though.
Learn more about KVM here (pdf). ®