Heading in a different direction from its main rivals, Ubuntu Linux will use
Red Hat Enterprise Linux and Novell's Suse Linux Enterprise Server both use the Xen virtualization software, a "hypervisor" layer that lets multiple operating systems run on the same computer. In contrast, the KVM software runs on top of a version of Linux, the "host" operating system that provides a foundation for other "guest" operating systems to run in a virtual mode.
"We've chosen to settle on KVM as our main virtualization focus," Soren Hansen, the Ubuntu Server Team's 26-year-old virtualization specialist, said in the Ubuntu Weekly News.
The move gives new prominence to KVM, which was initially popular with Linus Torvalds and other programmers of the Linux kernel. However, in the months since start-up Qumranet began the KVM project, the Xen programmers have made more progress in dovetailing their code more closely with the Linux kernel. KVM and Xen both are open-source packages.
KVM will be built into Ubuntu's next version, called Hardy Heron and due in April. "For the Hardy Heron release, we've really picked up the virtualization ball. Virtualization is making its way into data centers and onto developer workstations everywhere. Even 'regular' users are using it to run Ubuntu on Mac OS X all the time," Hansen said. "Virtualization has been on our agenda for a long time, but it became a top priority at UDS (Ubuntu Developer Summit) in November. We could see that demand for it was growing."
Canonical, the commercial sponsor of Ubuntu, will provide long-term support for Hardy Heron that lasts five years for servers and three years for PCs. Ubuntu is updated about every six months, but Hardy Heron is only the second version to get long-term support.
Xen is already built into Red Hat and Novell's Linux products, and Microsoft is on the brink of releasing its own virtualization product, called Hyper-V. However, the market leader for virtualization is EMC subsidiary VMware, which sells not only the virtualization foundation but also higher-level tools to monitor server performance and to move applications from one server to another to adjust work load.
Hansen said programmers also evaluated several other options, including Xen, Parallels' OpenVZ, KQEMU, and VirtualBox. "We found that KVM was the best fit for us right now."
Unsurprisingly, Xen fans see things differently. In particular, Simon Crosby, chief technology officer of Citrix Systems' virtualization and management division, said KVM's approach is better suited to desktop machines than to servers.
"Ubuntu is not widely deployed in enterprise data centers, where the need for a comprehensive virtual infrastructure layer independent of any guest operating system...is a requirement articulated by every customer," Crosby said in a statement. Ubuntu is widely used on desktops, so for Ubuntu programmers, "it seems natural that a hosted virtualization model makes sense to them."
Although Ubuntu didn't use the same virtualization foundation that dominant Linux seller Red Hat chose, it will use the libvirt package Red Hat created to provide a neutral management interface to Xen, KVM, or other compatible virtualization systems.
To provide an easier interface to libvirt, Ubuntu will employ software called virt-manager, Hansen said. "It allows you to set up new virtual machine, see which ones are running, and how much CPU they're consuming," he said.
Intel plans to launch an effort called LessWatts.org on Thursday, a combination of open-source software and helpful hints to reduce power consumption of Linux servers, PCs and gadgets.
LessWatts, to be detailed during a Intel Developer Forum speech by Renee James, vice president and general manager of Intel's Software and Solutions Group, is geared toward technically sophisticated folks from programmers to system administrators. It gathers together a number of Intel projects, such as the PowerTop utility for finding which software is pestering the processor and preventing it from dozing in low-power states.
Taking Intel's advice and fixes can trim about 10 watts of power consumption off a modern dual-processor server, said Dirk Hohndel, chief technologist of Intel open-source technology center. That's not a gargantuan amount--until you consider that if done correctly it's free power savings, that each watt of server energy saved cuts another 1.3 watts from air conditioning (according to Intel figures), and of course that 10 watts per server is a lot when multiplied by the thousands of servers that populate larger data centers.
Announcements of open-source contributions often carry an altruistic flavor, but don't believe for a minute that Intel is acting out of the goodness of its own heart. It would dearly love to make its server technology customers happier, and lower power consumption can help bring the chipmaker's vision of mobile Internet devices to fruition by extending battery life.
On a current laptop, running Fedora 7 from Red Hat uses about 21 watts. "If you apply six little changes we propose, that same laptop takes 15.5 watts," Hohndel said. "You have just added a more than an hour to your battery run time."
Intel is cooperating with various programmers and Linux sellers, so it's likely that some of its suggestions will be incorporated into standard software.
Pardon me while I nerd out here a bit, because I find this stuff intriguing. Here are some of the particulars of the work that Hohndel detailed:
• "Race-to-idle" changes to the Linux scheduler, a component of the kernel that decides what the computer is concentrating on at any given moment. Processors actually consume less power if working in bursts of business followed by cooler, idler moments than if working at a constant pace, and scheduler changes can encourage this hurry-up-and-wait philosophy.
• Compressed data in graphics-processor communications. The memory interface consumes power when transferring data from memory to the graphics chip, but it takes less if that data is compressed, and graphics chips have built-in abilities to decode that data. It takes power to decode--perhaps thousandths of a watt--but a half a watt can be saved in memory interface, Hohndel said.
• Changes to higher-level software. One example: Linux has software to mix sounds such as system beeps and music useful on desktop machines, but that software often is installed on servers with basic sound chips that typically aren't used. And the sound mixer checks 50 times each second to see if somebody has fiddled with the volume control, prodding the processor into activity each time.
• Dialing down network transfer rates. Dropping down from 1-gigabit-per-second Ethernet to a tenth that speed can save about 2 watts. "If you know when your link is needed and when it's idle, you can save power," Hohndel said.
• The tickless Linux kernel This approach essentially trims out the processor busywork of checking for things to do regularly, instead letting it drift off into low-power states and then wake up when there's work to be done.
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