Red Hat Inc. will be packing the next update of its new operating system release, Red Hat Enterprise Linux 5, with broader virtualization support, said Red Hat's Emerging Technologies Group consulting engineer Jan Mark Holzer in a session on virtualization best practices. His co-presenter was John Shakshober, Red Hat consulting engineer.
RHEL 5.1 will bring hardware virtualization feature improvements, paravirtualized drivers, the Xen 3.0.5 hypervisor and features like non-uniform memory access (NUMA) topology and loopback removal. Also, 5.1 will support live moves of virtual machines in clusters, along the lines of the functionality of VMware's VMotion.
In future updates to RHEL 5, said Holzer, Red Hat will offer support for a common virtualization infrastructure, more features for libvirt (a C toolkit), LAN and storage management APIs and support for KVM in Fedora Core 7.
Users of older versions of Red Hat are not being left out of the virtualization loop. Just last week, Red Hat added some Xen support features to Red Hat Enterprise Linux 4.5. "This was really needed by Red Hat users, many of whom have not moved to RHEL 5 for various reasons," said Summit speaker Bernard Golden in an interview following his presentation, "Succeeding with Open Source Virtualization."
For example, at Bucknell University in Lewisburg, Pa., updating to RHEL 5 has been delayed due to a lack of legacy application support, said Jeremy Dreese, systems integrator, engineering computing support team (ECST). His department is still using RHEL 3, largely, and doing virtualization in a small way on faculty desktops.
The 4.5 option will have limitations. "RHEL 4.5 includes virtualization support, so you have the choice of full virt or paravirt," said Red Hat consulting engineer John Shakshober in a best practices session. "Anything prior to RHEL 4.5 will run out of the box but will need full virtualization. You'll need a new chip. You don't have to touch the code, but you won't get the performance you get with RHEL 5."
Such tradeoffs are common in the virtualization arena today, as one platform may work well in some situations and another in others, said Golden.
"VMware is way ahead of all the others in features and robustness," said Golden, "but VMware doesn't have a product that scales well." There are definitely limitations in high-availability, he said, so most people are just virtualizing file servers at this point and not databases and performance-intensive apps.
User John Paul Barraza of Systran Software Inc. noted that, "VMware told us not to virtualize their high-CPU-load applications on ESX because we wouldn't get good performance." In general, he said, virtualization platforms can't scale well and are plagued by poor I/O issues. He'd like to use Xen, but it's not robust enough and lacks the advanced features of VMware's products.
Golden noted that Xen was way behind VMWare on ease of management and configuration. "Frankly, neither Xen nor Microsoft is anywhere near VMware," he said in a post-session interview. "Microsoft is coming out with stuff on Longhorn, but it has a big gap to close. Ninety percent of users I talk to use VMware."
To get the most out of RHEL 5's virtualization support options, Shakshober and Holzer had these recommendations:
- Secure RHEL 5 platform layer before installing any virtual machines or applications.
- Run SELinux to run in enforcing mode.
- Remove or disable any unwanted services, like AutoFS, NFS, FTP, WWW, NIS, telnetd, sendmail and so on.
- Only add the minimum number of user accounts needed for platform management.
- Avoid running applications on dom0/Hypervisor, because running apps in dom0 may impact virtual machine performance.
- Use a central location for a virtual machine installation, which will make it easier to move to shared storage later on.
Virtualization is still a nascent technology, so don't rush into it, Golden said. "Virtualization affects all parts of the infrastructure, and there are a lot of options available today. Assess your goals, existing infrastructure and organization's skills before implementing," he said. At this point, the safest route is getting started with VMware, said Golden, and added, "Xen will come along quickly, but it's not ready for production use today."