Size of volume on a file server

I will be setting up two (virtual Server2008R2) file servers in a failover cluster. The size of the data disk will be 3TB. Is it best to split up the disk in 2-3 volumes, or should I just go with a single large volume?

I will be using IBM Tivoli Storage Manager for backup purposes. Will a single large voulme have any impact on the backup/restore process?