LVM2 Metadata Copies- How Many and Performance hit?

[dman777]

I'm going to by making a lvm2 system with just one large partition. This is for my KVM guests...one will be a websever and the other will be a mysql server. I am trying to decide if I should use 1 or 2 copies of metadata for the PV and also the VG.
1)If I use 2 copies of metadata on the PV and also the VG, will there be a performance hit?
2)How likely would the metadata on a LVM2 PV and VG get corrupted?
3) When I do snapshots, does the PV and VG metadata get backed up also?