WD GreenPower disks have some problems under Linux with their “head parking” feature parking the head every 8 seconds. This destroys the disk over a short time span. For Linux, there's idle3ctl from the idle3-tools.
You can display the current value with the following command:
$ sudo ./idle3ctl -g /dev/sdX Idle3 timer set to 80 (0x50)
The value 80 means 8 seconds (default). From 1-128, the values mean 1/10th of a second, e.g. 128 would be 12.8 seconds. 129-254 are in 30 seconds steps. 129 is 30 seconds, 130 is 60 seconds, etc.
Set the desired value as follows:
$ sudo ./idle3ctl -s 158 /dev/sdX Idle3 timer set to 158 (0x9e) Please power cycle your drive off and on for the new setting to be taken into account. A reboot will not be enough!
Do as it says to enable the new setting.