It seems Windows 8.1, and possibly other versions as well, may well ignore its current Power Management Advanced Options settings for USB Selective Suspend.
 
I recently had added a USB 3 4-port hub to a desktop of mine, and two times it suspended the devices I had attached through that hub, which were my mouse and keyboard, and they were toast.
 
So, I went in to double check my settings, and indeed, as I have done for many years now, almost always one of the first things after loading up Windows on a new build, I HAD gone into Advanced Power Management Options and disabled the USB Selective Suspend, and yet the newly-added hub had its devices shut off anyways.
 
I went in through Device Manager, and discovered that when I added the new USB 3 hub, Windows gave it a Power Management option to turn it off to save power, even though the Selective Suspend was in fact Disabled.
 
SOOOO - Windows ignores the current USB Selective Suspend settings from Power Management Advanced Options, when installing and enabling a new USB Hub.
 
Hope that helps somebody, sometime, somewhere.  :)
 
Bob Bone

Bob, 
I think this is going to help me. Do you need to go and set it somewhere per USB drive if it's ignoring your global option?

 Well, there is an option in Control Panel Hardware and System in the Power Plan Advanced Options, where you want to find the parameter under USB Settings, and when you open that up you will see Selective Suspend - set that to Disable.
 
Another place to check/set is through Windows Device Manager, and THIS is where I went to change the default behavior for the new USB 3 hub that I had added to my system AFTER doing the Power Management Options change to USB Options - Selective Suspend.
 
So, an easy way to get to Windows Device Manager is to open up an instance of File Explorer, then right-click on This PC (Windows 8.1) then click on Manage, then when Computer Management opens, click on Device Manager.  (OR, go to: Control Panel\System and Security\System and then click on Device Manager)
 
Once in Device Manager, go down to the Universal Serial Bus group and expand it, then double-click on each HUB to open up its properties.  Click on the Power Management tab and remove the check from the option to Turn Device Off to Conserve Power and click OK.  You would make this change only for each HUB, not for each device.  If when you open Properties you do not see a tab at the top right of the properties dialog box, then you are looking at a USB device and not a USB hub.
 
In addition, Windows also maintains a setting for Power Management in the properties of any Network Adapters, so you might want to open the properties for any of those as well, and remove the Power Management tab's check in the box for the option to Allow Windows to Turn off Device to Conserve Power.
 
I hope the above helps, 
 
Bob Bone
 

Win10 does that to me with an external usb3 drive so now I use KeepAlive HD to keep it from going to sleep.

I had no idea those settings where in the Device Manager - thanks for this!

smallstonefan
I had no idea those settings where in the Device Manager - thanks for this!

There are TWO places you can look:
 
1.  Device Manager, expand Universal Serial Bus Controllers and double-click on each HUB, then click Power Management tab in the Properties dialog, remove check for option Allow Windows to Turn Off Device.....
 
2.  Control Panel>Hardware and Sound>Power Options - choose High Performance Power Plan, apply/save, then click on Change Plan Settings, then click on Change Advanced Power Settings, then expand USB Settings, then expand USB Selective Suspend Setting, then set to Disabled.
 
If you have not done so already, I also recommend while in the Power Plan settings to change it so your computer NEVER goes to sleep or turns the hard drives off, and I also always set the Minimum Processor State to 100%.
 
I hope all this helps you out.  I wish I knew what you do for Windows 10 and power management there.
 
Bob Bone
 

Hey - I just looked up the Windows 10 steps to change USB Selective Suspend, and it looks like it might be the same as I described above, so please review what I posted and give that a shot, so that you don't have to keep using that keep drive alive or whatever that little utility is.
 
Bob Bone
 
 

I made the changes - thanks again!