Bought my EX4 last week together with 4x6 TB WD Red drives (not Pro). Bought the drives separately to get 3 years of warranty - apparently you only get 2 years if you buy the box with the drives already installed, which I find a bit odd.
Created two RAID 1 volumes and have been backing up several TB. During the process I noticed that the box got rather hot after some hours - up to 58 degrees C (only 1 RAID volume in use at any time). Looks like the fan is totally out of sync with the temperature. Examples:
43 degrees / 1110 RPM
47 degrees / 1110 RPM
55 degrees / 900 RPM
56 degrees / 870 RPM
58 degrees / 1065 RPM
This makes no sense. Is the box defective or what?