The System Volume

The system volume is a regular static or thick volume that QTS uses to store system data such as logs, metadata, and thumbnails. By default, applications are installed to the system volume. If no system volume exists, either because the NAS has recently been initialized or the system volume was deleted, QTS will assign the next static or thick volume that you create as the system volume.

Important:

QNAP recommends creating a system volume of at least 10GB. This is to prevent errors caused by insufficient system volume space