To copy a backup of a large database over a WAN, I recommend the following:

1. Make a compressed backup of the database to multiple output files. Example: Make 20x5 GB files, instead of 1x100 GB file. The compression and multiple output file options are available with the BACKUP command.

2. Setup multiple streams of file copies so that you are copying multiple files at a time, say 5 in parallel. This will help to make sure that the WAN pipe stays full.

3. If possible, make sure that the source and target machines for the file copy are running Server Message Block (SMB) 2.0 or higher protocol (Windows Server 2008 and above, Windows Vista, Windows 7, Windows 8) . There were big enhancements to this protocol that dramatically improve performance on high latency links (WAN connections).