Virtualization, RHEL 5.1

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.

Users of older versions of Red Hat are not being left out of the virtualization loop. Red Hat added some Xen support features to Red Hat Enterprise Linux 4.5.


The 4.5 option will have limitations. RHEL 4.5 includes virtualization support, so you have the choice of full virt or paravirt. 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.

VMware is way ahead of all the others in features and robustness, but VMware doesn't have a product that scales well. There are definitely limitations in high-availability, so most people are just virtualizing file servers at this point and not databases and performance-intensive apps.

To get the most out of RHEL 5's virtualization support options, 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.