If you want to try out some cluster configurations, VMWare server has a nice feature where you can share a vmdk between more than one VM, and since it support SCSI persistent reservations, you can truly simulate a real cluster. I have used this to deploy Redhat Cluster server as a test environment.

After installing a new Gentoo server running rrdtool-1.3.8 and munin-1.3.4 I received many mails from munin's cronjob, complaining the following
(process:22748): Pango-WARNING **: Invalid UTF-8 string passed to pango_layout_set_text()