Buffalo Technology TeraStation Pro II TS-HTGL/R5 - Manual (Page 33)

Advanced Settings
To configure an unconfigured array, begin by double clicking on
the array you want to configure, e.g. “RAID Array 1”.
Choose your RAID mode under RAID Settings and put checks
next to the hard disks you want included in the array under
Disk Structure. Click Setup RAID Array when ready. It may take
several minutes to complete setting up the RAID array. When
it’s finished, a Disk Check will run.