Red Hat has taken its first step toward offering an alternative, open source virtualization environment for the enterprise.

Red Hat Enterprise Linux 5.4, the latest release which became available Wednesday, includes the KVM hypervisor, extensively tested for enterprise use. KVM stands for Kernel Virtual Machine.

The inclusion of KVM in Red Hat's 5.4 release reflects that firm's expected move away from the Xen open source hypervisor to the product it obtained with its purchase a year ago of the Israeli company, Qumranet.

Unlike other hypervisor suppliers, Qumranet had designed one that could be built into the Linux kernel. It is expected to gain operating efficiencies from inside the kernel, since it uses the kernel's scheduler and memory manager.

"The architectural advantage manifests itself in virtual machine performance and scalability," said Navim Thadani, senior director of virtualization. As it comes out of the gates, Red Hat's KVM supports a virtual machine making use of 16 virtual CPUs. VMware's vSphere 4 has a limit of eight. Like VMware, a KVM virtual machine may have up to 256 gigabytes of memory; the host server on which it sits may have up to a terabyte of memory.

Thadani said KVM in the 5.4 release was capable of hosting large number of virtual machines per physical server, "in the 90s, in some cases," he claimed, although details of what types of compute-intensive applications and amount of I/O required wasn't disclosed. KVM is capable of running applications provided by SAP and Oracle in its virtual machines, he said.

Red Hat's virtualized environment, however, is still at an early stage. It envisions four components; only virtualization as a feature of Enterprise Linux 5.4 is available now.

Red Hat anticipates making the KVM hypervisor available outside the operating system as a stand-alone product, the Red Hat Enterprise Hypervisor. It's also planning to launch the Red Hat Enterprise Virtualization Manager for Servers as a central console for managing KVM virtual machines. The fourth component will be a virtual desktop infrastructure, also based on KVM.