I want to store my XEN machines into an LVM group and have a server with a 500 gb drive.
How much place should i leave for the host system? i was thinking of 50 gb for the host system and the remaining for the lvm group… but maybe i need more on the host when doing lvm snapshots? Or are the snapshots stored on the lvm group anyway?
I use 30GBfor the host system & 10GB for XEN templates since I don’t do LVM snapshots but rely on the guest OS’s control panel to perform backups.
But, with LVM you could resize your partitions very easily 
i.e. if /, /var, /home, etc gets too big, just add more space