[SAC] Virtual Machines for Services

[Mateusz Loskot]

Frank Warmerdam wrote:
>
> I understand that Xen requires kernel modifications, and doesn't work well
> with some older systems.  Who is familiar with those limitations?  For
> instance, I'd like to be able to run VMs on "osgeo2" but I think it is
> running a somewhat antique RHEL, is that right?  Will it support Xen?
> Can we even run the vmware player on it?

Frank,

There is one essential difference between VMWare-like and Xen-based
solutions. The former is real virtualization and the latter is
paravirtualization or hardware-based virtualization.

Using VMWare is easier because it can host almost any operating system
without dedicated hardware or modifications of OS code.
According to documentation, Xen solution needs that guest OS is "aware of
being virtualized" so it requires modification of OS code.
Or, in order to achieve full virtualizationw and without modifying
guest OS, Xen requires special hardware features (Intel and AMD
virtualization features).

Xen solutions seems to be less universal but hardware specific, so Xen
performs better. VMWare, Parallels are easier to setup, do not require any
specific hardware and can run unomidifed guest OS, so they perform
"slower"
or require more resources.

This is my understanding of essential differences between Xen and VMWare.

Cheers
-- 
Mateusz Loskot
http://mateusz.loskot.net