QNAP has limited the amount of resources dedicated to their NAS lineup when rebuilding a RAID array or performing rsync backups.  The decision here was to limit the amount of impact these types of processes have on your system in order to maintain an acceptable level of responsiveness. This is very considerate of QNAP, however, I prefer a bit more control over my system and would like these processes to complete faster; well-knowing I will be sacrificing system responsiveness.