I just purchased a TS1400R 4-drive TeraStation without hard drives and will be purchasing 4 hard drives to populate the NAS unit.
Looking at the specs it appears that the original unit was sold with only up to 4TB capacity drives yielding a 16TB total effective capacity.
However, I'm wondering, with the latest Buffalo firmware updates for the device, if the TS1400R will support up to 8TB hard drives.