We tried something similar when using VM's for the repository and the 2TB VMDK limit in ESXi 5.0
I can comment on the performance, but i found overall management and maintenance a pain.
Have you thought of using SOBR? (Scale Out Backup Repository). Essentially this provides you the similar functionality by storing different backups on different volumes/partitions. The only difference is you are allowing Veeam to manage this process rather than Windows