@savvysps
I was using my Western Digital 2.5 inch 1TB SATA 2 drive with a SATA to USB3.0 adapter, and my iPad 2 charger to power all of it, and didn't need to worry about disconnecting the power (the Apple charger) when the hard drive was connected.
Then when re-powering it again, it all booted up without issues.
Just make sure there's no write activity going on with the drive, before you remove the power to the HooToo and it's connected drive.
It's similar with using a USB flash drive...the HooToo powers down or up with anything connected and let's it access the drive with no issues again.
You may find you'll need a bit more current (amps of power) for the USB connected hard drive than you did if you tried a flash drive on the USB port...and if it's a 3.5 inch drive you need to attach, that works too, you just need a power adapter that will support everything you want to connect to the HooToo nano if the power will be coming from the nano USB port, to power the device.
There is a limit though, because the HooToo can only support so much current running thru it to power it from its USB port.
In that case you'll need to use a separate power adapter for the higher current drive you attach to it, that is connected separately to that drive, like a DVD ROM drive, ...etc.
If you plan to just power down the hard drive, and keep the HooToo nano on, the same applies.
Make sure no write activity is going on before powering it down...but it's all do-able.
(Last edited by HooTooJunkie on 19 Oct 2015, 22:54)