I'm planning to deploy on a small server using KVM our old server for a small community group

the server has 2.3Ghz dualcore Xeon, 8Gb ram, 300Gb RAID1 Hard disk - no real budget for additional storage

Plan is to deploy this on KVM - also need a Vibe install on the same server - so host and 2 VM's
current User Data is 30Gb

Usually with OES I allow 80Gb (500Mb Boot, 4Gb Swap, 20Gb /, 15Gb /var and rest as home which stores install files etc)

which I know is OTT but in this case would leave me very for data!!!

What is practical for "small" OES VM & Vibe ?