OTG Cable and external drives

Til New Member Posts: 19
edited December 2016 in Peripherals
Hello everyone,
I noticed that the USB OTG cable in the shop has an additional USB A plug. Why is that?

Is this needed to supply enough power to whatever device may be connected there?

I'm thinking about combining my UpBoard with a small 2x2.5" RAID (fanless!) like this

So could I use an 3.0 micro-B > 3.0 micro-B cable to use this RAID with the UpBoard?

And would I need an extra power supply for the RAID in this case?
(Vendor: "USB bus powered included (Support up to 5V/3A), no adapter required" <-- is this realistic for the UpBoards OTG port?)