What is the necessary minimum root space to reserve?

[mmenaz]

Hi, in the "old days" the root space was necessary for the snapshot openvz backups (AFAIR files were copied there and then the backup file was generated, see --tmpdir parameter). I don't use openvz anymore, only kvm vms, and probably in any case things changed after 1.5 release.
So the question is, since proxmox installation takes only about 2GB of hd space, what is the "reasonable" minimum to reserve for root partition that does not have drawbacks or impact performances? I've the feeling that the default one is far above the needed (i.e. in a 1TB installation is 95GB, only 3% used).
Especially when using ssd, the more free space for VM usage, the better!
Thanks

 

[mir]

This is my default partitions:

Filesystem                                              Size  Used Avail Use% Mounted on
udev                                                     10M     0   10M   0% /dev
tmpfs                                                   1.6G  544K  1.6G   1% /run
/dev/disk/by-uuid/f66cdc9c-9cf8-4c31-802d-21b9ffcf0493  9.2G  4.2G  5.0G  46% /
tmpfs                                                   5.0M     0  5.0M   0% /run/lock
tmpfs                                                   4.7G   59M  4.6G   2% /run/shm

I think root could easily be shrunk to 6 - 8 GB