Just moved away from my Synology NAS after a bad experience trying to get files off it when the hardware failed - total pita!
I've got the following drives in a pool with folder duplication set on most folders:
2 x 4Tb
2 x 3Tb
..12.8Tb currently free, duplication free, nice green bar. It's not balancing any of the files to one of the 3Tb and one of the 4Tb drives though. Is this normal? Is it just not bothering as there's so much free space elsewhere?