Why?

Even though the Wii U has a built in SD slot, it doesn't support using it as a storage expansion to store Wii U games (unlike it's predecessor). USB pen drives are notoriously unreliable and hard drives are bulky and require extra power or a Y cable, using up multiple ports. Today big reliable SD cards have become cheap. Since a SD is needed anyway for homebrew, it would be nice to use that too as storage for games.
There have been solutions in the past like Loadiine, but this had various problems, the biggest of them performance and is not longer supported by current homebrew environments (Aroma).

SDUSB

SDUSB solves these problems. It uses a second partition on the SD card, which will be formatted to the Wii Us native file system and therefore run at full speed. The partition will show up as a USB device and can therefore be managed using the built in Data Management in the system settings. SaveMii, WUP Installers etc. all work with this, like it is a USB storage device. Also HAI (VC Wii Titles) work with SDUSB.
SDUSB does all that by patching IOSU (the OS that runs on the ARM processor). It is implemented as a stroopwafel plugin.

If you instead want to partition your USB HDD to use it for Wii U games and other stuff look here: https://gbatemp.net/threads/usb-partition-use-partitioned-usb-hdds-with-the-wii-u.656209/

Prerequisites

You need two things:

1. a way to launch minute
2. a reliable SD card

For 1. the recommended way is to setup ISFShax, for that we have a guide here: How to set up ISFShax
If you don't want to commit to installing ISFShax yet you can skip the "Installing ISFShax" step in the ISFShax setup guide and instead run it manually through the chosen exploit on every reboot.
Instead if ISFShax you can also use defuse, in case you have that already.

For 2. It is highly recommended that you use an Endurance branded SD card from a reputable brand. Since your save games will also be saved there, you rather want to spend $5 more then to lose all your save games because your cheapo sd card died. Also be aware of fakes, even on Amazon you can get fake SD cards...
The speed of the SD card isn't too important, as the Wii U is limited to 25MB/s (same as the internal memory) anyway. Every somewhat recent SD card should be able to get that speed. Choose Reliability > Access Time > Throughput.

Setup

Partitioning the SD card​

On Windows you need to use a third party tool like Minitool Partition Wizard or Easeus, on Linux you can use gparted.
You need to have two primary partitions on the card:

1. FAT32 - (in gparted set lba flag). This is what the PC will see and all your homebrew goes (you should already have this)
2. NTFS - This partition will be the "USB", you use to store the Wii U games on (don't assign a drive letter)

Shrink the existing FAT32 partition to make room and then create the primary NTFS partition after it. It's recommended to align the Partitions on 64MiB boundaries and use a multiple of 64MiB for the size. NTFS won't be the file system the Wii U will be using, it is just there to tell SDUSB which partition to use (it will pick the first NTFS one). The Wii U will later format it with it's own file system.

​

Installing the Plugin​

Get the latest wafel_sd_usb.ipx from here: https://github.com/jan-hofmeier/wafel_sd_usb/releases and place it in your ios_plugins folder. That is either wiiu/ios_plugins on the SD card or /sys/hax/ios_plugins on the slc. For slc you have to rename it to something shorter like sdusb.ipx

Using SDUSB

If you now boot boot back up, the Partition shows up as a USB device, which needs to be formatted and can then be used as usual. After formatting the SDUSB, you can also connect an existing USB storage and copy stuff over.

Known Problems

• GC VC Injectes don't work when installed to the SDUSB (they still work from Internal Memory)

 

[Blythe93]

Does the Fat32 partition only need to be 64 mb?

It... can? Provided you can fit everything you need for your CFW on that small partition. As SDIO mentioned in the guide, it's recommended to align the partitions on 64MiB boundaries and use a multiples of 64MiB for the size. If Wii VC games work, you've done it correctly.

I've personally used 128GB (~119GiB) microSD card, so I've left around 19GiB for the FAT32 partition and the rest for SDUSB storage.

 

[KelSolaar]

It... can? Provided you can fit everything you need for your CFW on that small partition. As SDIO mentioned in the guide, it's recommended to align the partitions on 64MiB boundaries and use a multiples of 64MiB for the size. If Wii VC games work, you've done it correctly.

I've personally used 128GB (~119GiB) microSD card, so I've left around 19GiB for the FAT32 partition and the rest for SDUSB storage.

Ah so the Wii games are stored on the Fat partition and Wii U games on the other one?

 

[Blythe93]

Ah so the Wii games are stored on the Fat partition and Wii U games on the other one?

I haven't tested Wii games on the FAT32 partition yet as I don't have a big enough SD card to test everything, but as far as I know latest USB Loader GX and Wii Flow should be able to launch games from your SD card. Just make sure that you get a quality endurance SD card for this setup.

As far as Wii U games go, I haven't noticed any issues or slowdowns. Too bad that transferring games from an external HDD to SDUSB storage takes a very long time (took me around 3-4 hours for around 70GB worth of games).

 

[Stan4d]

Is there a way I can partition the SD card on MacOS?

 

[SDIO]

The Disk Utility should be able to do that. If Mac OS can't create a NTFS partition, you can also create an exFAT one, it should have the same ID as NTFS

 

[Stan4d]

Later in the future maybe.. could someone make a more comprehensive guide for noobs like me who want to be able to do this?

 

[Blythe93]

Later in the future maybe.. could someone make a more comprehensive guide for noobs like me who want to be able to do this?

It's as comprehensive as it can get, I guess? I followed along the guide, had Tiramisu/Aroma previously so I've followed that path. Run into no issues.

 

[lordelan]

Later in the future maybe.. could someone make a more comprehensive guide for noobs like me who want to be able to do this?

I didn't do this on my own yet but it sounds very easy to do.
Just ask here if something's not clear and we'll help u out.

 

[Stan4d]

What can I do? Disk utility wont let me partition the SD card

 

[SDIO]

You probably need to unmount it first. Then you should be able to shrink the FAT32 partition

 

[Stan4d]

The option is still greyed out.

 

[SDIO]

Maybe you can do it on the command line tool with diskutil.
Or you might be able to find a third party tool which can do that.
Else it would probably the easiest to use another computer or to boot a Linux with gparted.

I don't have a Mac, so I can't test it

 

[ItsGameBoy]

I've been trying to use Minitool Partition Wizard when following this tutorial, but whenever I try to apply those changes (resizing the FAT32 partition, creating the NTFS partition from the unallocated space), I keep getting "Error Code 12," which is a filesystem error according to their website. I tried using the "Check File System" option in the application to see if there were any problems, but no errors were detected, so I don't know where to go from here.

I am using a Kingston 64GB Canvas Select Plus microSDXC Card. I know this is not an endurance-based SD card, but I really want to try this out.

 

[Stan4d]

Maybe you can do it on the command line tool with diskutil.
Or you might be able to find a third party tool which can do that.
Else it would probably the easiest to use another computer or to boot a Linux with gparted.

I don't have a Mac, so I can't test it

I will just use a third party software instead

 

[ShotSkydiver]

I've got everything setup and working great with my 128GB SD! Thanks for the extremely clear and well written guide, it was easy to get it working! The only "issue" I've noticed is that the Wii/GameCube WUP games that I've generated via the TeconmoonWiiVCInjector tool and installed via WUP Installer GX2 causes the WiiU to reboot upon launching them, which just takes me to the minute screen, which just autoboots back into the WiiU menu, is that more of an issue with minute or an issue with the forwarders?

 

[Blythe93]

The only "issue" I've noticed is that the Wii/GameCube WUP games that I've generated via the TeconmoonWiiVCInjector tool and installed via WUP Installer GX2 causes the WiiU to reboot upon launching them, which just takes me to the minute screen, which just autoboots back into the WiiU menu, is that more of an issue with minute or an issue with the forwarders?

I haven't tested VC injects yet, but SDIO mentioned int the first post that, when creating partitions, it's recommended to align them on 64MiB boundaries and use a multiple of 64MiB for the size. He mentioned that even MB alignment should be fine, even more so if the WIi VC titles work.

 

[SDIO]

Check if the forwarders work from internal memory. It might be just an incompatible SD card

 

[FRKN4O]

What do I need to do now?

 

[SDIO]

you shrink D: and then create a new primary NTFS partition after that.

 

[4d1xlaan]

would it be possible to use a similar concept to patch ios to allow partitioned hard drives, so you could have one fat32 used by vWii and one wiiu partition for installing wii games?

https://gbatemp.net/threads/using-a-single-external-partitioned-hard-drive.656012/

so the same thing as this, except instead of sd storage it's usb storage