As far as this is concerned
Currently its:
Maximum size of file depot = 5GB
Minimum free disk size to create new file depot = 2MB
Amount of disk space which should stay free on disk = 0MB
Event if the free disk space drops below = 10%
These are optimal values. I have had a number of peopke tell me that if they increase the "Maximum size of file depot", it actually slows down the backup
All Backups to a D2D device, whether a File Library or a VLS, should run with a concurrency of 1 (default is 4)
I may have something else to offer if you start getting errors "{64] Network Path Not Found" on your media agent, this has been an ongoing issue when using Network-Attached Storage as a File Library repository, and is actually a Windows limitation