Buffalo DriveStation Duo User Manual page 6

Using the RAID Utility
Select the drive structure that you'd like to use. Click Yes, Yes, and OK.
Understand that this will erase any data on the drive!
The disk structure will be rebuilt and automatically formatted with
FAT32. FAT32 is compatible with Windows PCs, Macs, and Linux. If
you would prefer to use NTFS formatted disks, run Windows Disk
Management from the Disk Settings menu. NTFS is recommended for
video editing, backup, and other programs that generate files larger than
4GB.