[Answer ID: 14105]
Replacing a hard drive with higher capacity of drive in the TeraStation
It can be larger, but not smaller if it's part of a RAID 1 or RAID 5 array.
The extra space in the case of a larger drive won't be added to the total volume of the TeraStation.
If a smaller drive is used, TeraStation will reply with an error when an attempt to rebuild the RAID array.
It can be larger but Buffalo Technology do not support this, as there might be no possible usage of the extra space of the drive.
If you remove more than one drive at the same time, all data on the RAID array will be lost regardless of which RAID mode the TeraStation is in. This will void your warranty.
To preserve your data, replace drives one at a time, rebuilding the RAID array after each replacement.