USB flash drive (1TB) loading time to library

I had the latest version of 2.03 installed on my raspberry pi 3. I am using a 1TB flash drive with about 300GB of music files. The drive is formatted with FAT. How long does it take for volumio to scan everything to show up on the library ? I had waited for 1 hour and the scan still not showing all the files in the drive into the library. What should I do next ?