But Novell refused to quantify the performance improvement users should expect, other than to say it should be significant. "We're staying away from specific numbers," said Justin Steinman, Novell's director of marketing for Linux and open platforms. All applications should see performance benefits, although I/O-intensive applications will probably see the greatest boost, he said; VMI is about streamlining communication between the Linux kernel and the hypervisor.Al Gillen, a research vice president for system software at Framingham, Mass.-based research firm IDC, said that turning on VMI in SLES 10 might not only improve performance of individual applications but also allow users to run more virtual machines per VMware server. How many more will depend on the environment. "It's not always an easy thing to measure, because workloads vary," Gillen said. Not just paravirt_ops
VMware's VMI interface is part of Linux kernels based on version 2.6.20 and above, where it is known as "paravirt-ops." But because SLES 10 is based on the older Linux 2.6.16 kernel, Novell engineers had to integrate VMI into Novell's kernel themselves. "We actually had to do a fair bit of engineering," he said. As such, Novell becomes just the second commercial vendor to officially support VMI, joining Canonical Ltd., which supports VMI in Ubuntu's Feisty Fawn (7.04) and Gutsy Gibbon (7.10). But the VMI interface can also be enabled in any Linux mainline kernel version 2.6.22 or above. Novell customers that want to take advantage of VMI can simply upgrade to SLES 10 SP2, which became available in May, and turn it on using standard operating system setup and configuration tools.