@Pence_PC Kudos to figuring out the
very complicated way. There's a way simpler way to achieve dual HDD setup and here's how:
First, you'll need to set USB Loader GX accordingly: both
Loader IOS and
Game IOS should be set to
249. (WiiFlow users should have something similar in their settings as well.)
Second, you'll need two external storage devices,
one for Wii/GC games (referred to as vWii HDD, FAT32 formatted)
and the other one for Wii U games (referred to as Wii U HDD, formatted by Wii U's proprietary format).
vWii HDD's partition will need to be hidden with U-Stealth or similar application in order to hide the Wii U's format nag.
I personally use 2x ADATA SU650 960GB SSDs within USB 3.0 Logilink HDD enclosures connected to Wii U with USB 3.0 Y cable.
vWii HDD's data cable goes into the top back USB port, Wii U HDD's data cable goes into the bottom back USB port.
(Otherwise it won't work, I guess? Haven't tested thoroughly, but I think it could work provided you set up the USB Loader GX / WiiFlow properly afterwards to load the games from another USB port.)
For the Y cables' power cables, I bought 2x USB 2.0 cable extensions and I'm using external USB power adapter (3A/5V), plugged into a wall outlet.
Note: If you'd like use your Wii U's other two USB ports for additional power instead of using an external charger, it's important that vWii's data cable go into the top back USB port, Wii U data cable can go wherever you want it to go (I tried plugging Wii U cables in the front USB ports and everything works properly). If you go this way, you won't need an external power outlet, but you'll use up all of Wii U's USB ports (which you could use for other Wii U accessories like GC adapter.
Additional notes:
- I ordered some USB3.0 to SATA adapters, thinking that I might be able to just connect my SSDs to the Wii U and be done with it, no Y cables needed. While it did work for my older SSDs (Samsung EVO 850 240GB and Kingston SSDNow 64GB), it didn't work for the new ADATA ones. I run into all sorts of issues, but it might be related to the cables which are probably faulty. You could try with some reputable brands, if there are any. In the end, I gave up and ordered those Y cables and used the SSDs within enclosures that I know that will 100% work with dual HDD setup.
- Some enclosures won't work at all? Apparently vWii HDD can sometimes have initialization issues (source here), but I can confirm that USB 3.0 2.5in HDD enclosures by Logilink worked for me, both for vWii and Wii U HDDs.
- USB 3.0 cables and enclosures are probably overkill, plus USB 3.0 cables can interfere with Wii U's wireless connection. I run into that issue while I was trying to connected my Wii U to the router that was sitting right next to it. My Wii U HDD at the time was plugged into the back ports, alone, without vWii HDD when I tried to connect to the Internet. Temporarily I reconnected my Wii U HDD to the front ports instead of the back ones so that I could finish downloading stuff via NUSSpli. (After seeing how bad download speeds were, I bought an official Wii LAN adapter which doubled the speed which was a bit more tolerable, definitely recommended.)
- SSDs are probably overkill as well, you're probably better off with whatever you can find at an affordable price.
- In case you run into issues, always check if it's the settings first, cables second, enclosures third, HDDs fourth.
You can find more info about dual HDD setup
here.
It's also possible to get 2HDDs in one two bay enclosure to work, it just needs to have 2LUN mode. More info
here.
There's even 3 HDD setup, explained
here.