[CentOS] KVM resources?

Later this week I will have to install a serious KVM setup, and I am looking for background material.

I found a nice how-to:

http://wiki.centos.org/HowTos/KVM

...but it is probably partly outdated by now.

Then there is a fine virtualization manual:

http://www.centos.org/docs/5/html/5.2/Virtualization/

...but it seems to be only for xen.

I plan to use either CentOS 5.6 or Scientific Linux 6.0 as the host system. Though I don't know yet, if v6.0 will bring any actual benefits over 5.6.

My guests will all be CentOS 4 or 5. Disk I/O will probably be a potential bottleneck. I am interested in the "block device" strategy, and could use more info about it.

- Jussi