VSS and Failover Clustering

Hi,

I have a 4-node physical cluster.  External storage is fiber attached to an HP disk array.

The cluster runs about 25 virtual machines.  All the VM's are based on CSV's.

I'm trying to understand where VSS puts its snapshots, when it is dealing with a failover cluster with VM's.

Does each VM use part of its virtual disks, to store the VSS snapshot, or does the cluster snapshot each VM and add the VSS snapshot storage to the CSV's?

thanks for any help!

Mark