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Red Hat Enterprise Linux 5: All about Xen

It's no secret that Red Hat Enterprise Linux 5 has Xen built in. But what some users might not understand is just how much of an impact paravirtualization will have on Linux in the data center.

Experts, users and authors agree: When Red Hat Enterprise Linux 5 launches in February, it will succeed or fail on the merits of Xen.

Red Hat Enterprise Linux 5 at a glance:
Without a doubt, the most important RHEL5 feature is Xen. But other areas of focus include:
  • Network storage (Autofs, iSCSI)
  • Kexec / Kdump (replacing Diskdump and Netdump)
  • Smartcard integration
  • SELinux securityInstaller improvements
  • Clustering and cluster file systems
  • Analysis and development tools (SystemTap, Frysk)
  • Stateless Linux enablers
  • Infiniband and RDMA (OpenFabrics.Org)
  • New driver model for better integration of out-of-kernel-tree drivers

- Ken Milberg

Forget the FUD, said Andy Hudson, a RHEL 5 beta tester living in the U.K. and author of Fedora Core 6 Unleashed. Forget the deep support discounts offered by Oracle for its Unbreakable Linux, and definitely forget about the claims coming from the Microsoft-Novell camp about interoperability. They're all moot points.

All you need to know, he said, is that RHEL 4 was a solid operating system and RHEL 5 is going to knock people's socks off. And it's all going to revolve around Xen.

Xen, Xen, Xen

Xen is an open source virtual machine monitor for x86-compatible computers. It allows multiple guest operating systems to run on a single computer by using a software layer called a hypervisor to mediate access to the hardware. The hypervisor directs hardware access and coordinates requests from the guest operating systems.

RHEL 5 will incorporate Xen into RHEL 5 for fully integrated server virtualization functionality, said site expert Ken Milberg. Through Xen, open source virtualization allows enterprise users to utilize sparse capacity and provide increased availability to their systems. With Xen, Red Hat will save IT managers money by offering this capability without using VMware, he said.

RHEL 5 won't be the first commercial Linux distro to feature Xen. In July 2006, Novell added it to SUSE Linux Enterprise Server 10 (SLES10). At the time, experts called the move premature, and Red Hat executives bickered publicly with Novell over putting Xen in SLES10, saying it was too early to commit an OS to unproven technology.

But what was largely seen as Red Hat rhetoric now appears to be a strategic coup-de-grace, Hudson said.

"The extra time was definitely worth it. New additions like Virtual Machine Manager are simple little tools that go a long way towards getting Xen into the data center by making it more useful," Hudson said.

The Virtual Machine Manager (virt-manager) is a management application for virtual machines. It uses libvirt, a C toolkit for interacting with the virtualization layer, and it is capable of managing virtual machines running on any supported hypervisor. The application's views provide summaries and detailed statistics on performance and resource utilization. A wizard facilitates creation of new guest domains both paravirtualized and fully-virtualized. Console access is enabled either to a text-based serial console or fully graphical access via an embedded virtual network computing (VNC) client.

Linux, the virtual server standard

Russell Pavlicek, senior Linux architect at San Jose-based Cassatt Corp., said that while many organizations are already looking to market leader VMware for virtualization, others are just as curious about Xen. "Having Xen available with this release should jumpstart some of that activity," he said.

Xen could also jumpstart Linux as the platform of choice for server virtualization. Linux is already a popular option for IT managers who use it as a host for virtual machines in the data center. "Now that Xen will be available natively on Red Hat as well as other distributions [like Novell], the number of virtual servers hosted on Linux should leap forward," Pavlicek said.

Hudson isn't surprised that users are excited about what Xen can do for Linux.

"[Red Hat] has integrated Xen very well with this release. By the look of things, they are actually using an install key to define the class of the server installation. It seems they have included two server classes: a regular, general purpose server and a fully virtual server," Hudson said.

SELinux gets fine-tuned

SELinux, an implementation of mandatory access control using Linux Security Modules (LSMs) in the kernel, has earned a reputation for being hard to use and overly complex.

Red Hat was listening, apparently, and RHEL 5 includes a troubleshooting tool that helps IT managers understand how SELinux is controlling the system. "The troubleshooter really cuts through the mist around SELinux and allows the user to see what's going on," Hudson said.

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