WD makes a green devices which have optimized power usage. But this feature seems to bad working on Linux system. Problem is that the device makes a massive Load Cycle Count. Windows still using a drive, mostly with 1-2 seconds of break so on Windows it shouldn't be a problem. Linux using a drive sometimes rarely, 10 seconds, maybe more. The clue is that WD green stops/park it's head(s) by default after 8 seconds of no device usage. After one months Linux can make a Load Cycle Count approx. 50k times. Some sites inform that standard HDD drive can handle about 300k, then will be problem with warranty.
When using green devices on Linux, there a need to disable or extend time of such feature. There are two option to achieve it:
Just download the idle3-tools, compile, run it. Remember you have to shut down the server or restart you disk enclosure. Normal reboot is not enough. Drive need to be stopped, power down and and power up on to correctly read new settings from firmware.
smartctl -A /dev/sda | grep “^193”
Should be not changing when your Linux is on. When is changing then is something wrong, no shutdown?