NAS-Drives are very busy

[ix4Slow]

Hi to all,

Since a few weeks my ix4-200d has a very low response. According to the noise, and vibration I can feel with my hand on the case, the harddisks are very busy. I've got 4x 2TB disks and they are in RAID5 since I bought this NAS (some 3 years ago). I cannot figure out why this is happening or why this high activity take place. The Windows Task Manager or the Resource Monitor doesn't show the NAS-drives at all. The processor is almost doing nothing and there's plenty of unused memory. The Health-screen of the NAS itself shows everything is OK. There is no software busy processing anything and there is no download active with the torrent-client.
Is there any utility with which I can monitor the (source of) activity of the NAS disks?
Thanks for all suggestions.

[maozip]

in system management applications , stop securemindinstall or other app of video survelliance
The application to see the resources is resmon