Addendum: Plex now possible because the software chip architecture has been adapted. If you have a good media server, Plex is not necessary (play anyway no ribbed native DVD codecs with "original" menu structures). However, Deep Sleep does not work still if USB drives are connected to the backup. Thus, the power consumption in the idle state of the disks remains quite high. The fan is to constantly hear - it does not arise from the state of rest of the disks.
Bin but still excited about the functionality of the Synology DSM firmware. Therefore remain the 5 star. Runs on 4 WD Red HDD (respectively 3TB). Did not have a failure ...