How do I turn the damn external HDD off ?

Ok so yesterday I got me a spankin´ brand new 2.5" external WD 2TB HDD for my X1, plugged it into the USB port, formatted it, moved some games to it and .... how do I turn it off ( other than the obvious unplugging from the console ) ? The X360 slim keeps suppling power to the rear USB ports even when turned off so I have to unplug the external HDD when I´m done, doesn´t bother me that much but I was hoping the X1 had some way of not providing power to the USB when turned off. I looked at the energy and power options but there´s nothing there. Is there such a thing ? I have no problem at ruining the power supply in the X360 since the HDD is inside a "replaceable" 5 dollars case but in this case the situation is different, the HDD is not in a replaceable case.

So you're not going to use it as your main drive?

There is an option under the power mode section for Instant On, and it is something along the lines of "turn off storage device when Xbox is off". However, with my 4TB Seagate this function did not work properly(after my HDD would turn off, it would turn back on randomly after a few minutes).

Therefore, since then I simply leave my HDD plugged and on all the time, I read they have a very long life like that and I have had no issues but I'm not necessarily suggesting you do that....I got mine super cheap, so I don't care when it dies I'll get another better one. Mine has an external power adapter, so think that is why it would not auto shut off properly....but with yours it might work, you can try it. I would suggest if you use that function to closely monitor your HDD at first after your Xbox shuts off to ensure it is not acting up.

Turn your Xbox off all the way, otherwise if you're going to have it standby power down mode then it's going to have some limited functionality still as the console is still functional, downloading and installing updates to software and apps and such, even games you have set to download that might be queued up can install on their own while in standby mode, your game saves backed up to the cloud, whatever the console needs to do. You can always hard power down, i.e. hold the power button down 10 seconds until it shuts off for good.

I don't see what the deal is, the drive is quiet, I just leave mine (got same setup, WD external HDD 2TB), I just leave it plugged in and don't bother. Haven't had any issues leaving it like that.

Also by using Energy Saving mode(turns off Xbox completely, just like holding the power button) my HDD turns off completely by itself even while still plugged in. But most of the time I use Instant On and with that just leave my HDD plugged and turned on all the time basically.

It's not hurting the HDD to be on while using Energy/Instant-on mode. The only way for that to work is to keep all HDD's on while it's in standby. Not sure why you are stressing over this.

I have the same issue, my fix was to plug it in through one of those light switch type outlets. I would have to turn on both the xbox and the hard drive when using it. I eventually just do what it does and said whatever.