I've been successful in creating my first 'real' KVM/QEMU virtual machine. 'Real' because it's running something Freedom IT relies on for the day-to-day running of our business: Email.
Yep, Scalix is running on top of Centos 5.2 inside a virtual box inside a Centos 5.2 Host. And it's performance is fantastic.
Why KVM and not Xen?
I opted to create a KVM virtual machine as opposed to a Xen-based virtual guest since Red Hat seem to be heading in the KVM direction. And I am glad I did so since hearing they have acquired Qumranet.
Which type of disk did I use?
I chose to use a real disk-partition (as opposed to a file) and that partition is actually a mirrored device on the Centos Host
Why did I choose to virtualise the Scalix email server?
Well, previously I had it running on my underpowered Trixbox (PABX) PC. And while it was OK, I was never confident of it's successful restoration probabilities in the event of a catastrophic failure! Since Scalix includes numerous components (PostgreSQL Database, Tomcat, LDAP server) I thought it wise to give the software it's 'own' environment. So nothing else will run on that virtual server.
BTW, a really useful script I found while finding out how to transfer the existing Scalix data across to the new machine was sxstoreexp. This can be found here. And I'm going to use it for backup purposes on my customers sites too. It worked really well.