Hi,
When you change RAID configuration in a QNAP you might have sometime slowness during the Expand of the disk.
To improve the speed, log in the QNAP in SSH (Enable it first if disable).
ssh admin@your_ip
Type the command : echo 25000 > /proc/sys/dev/raid/speed_limit_min
You do not need to reboot or restart the Expand. This value will be taken on the Fly.
J