[Tutorial] How to install bootcamp/windows on SSD part of Fusion Drive

I have a 2017 (June) iMac 5K configured with the 2TB Fusion Drive. Initially, I installed windows using Bootcamp assistant but after using it I realized how slow the performance was in Windows. This is because by default Bootcamp will install Windows on only the HDD drive (slow) and won't benefit from the 120 GB PCIEx SSD (super fast).

Since I use both MacOS Mojave and Window 10 each 50% of the time, it was important for my to have good performance in both operating systems.

So in the end, I decided to split the fusion drive into the SSD and HDD and manage it myself.

Now, I have MacOS on 60GB partition of the SSD and Windows on the remaining 60GB partition of the SSD. I formatted the 2TB HDD as exFAT and named it WinMac, which I'm using as a big data drive for both MacOS and Windows. Now, its the best of both worlds - super fast boot up and fast operating systems and a super large HDD for data accessible by both.

Here's the basic steps I took to achive this configuration.

1. Backup all your data on an external drive and unplug it
2. Enter Internet Recovery Mode (Restart mac and hold Control + Command + R)
3. Go to Utilities -> Terminal
4. To find the Fusion Drive's disk name, type "diskutil apfs list"
5. Assuming the drive is disk0, type "diskutil apfs deletecontainer disk0"
6. Go to Disk Utility
7. Select the SSD drive and create 1 partition as APFS for MacOS, and an other partition as exFAT for Windows/Bootcamp.
8. Select the HDD and format as exFAT and rename as WinMac (your choice).
9. Exit Disk Utility
10. Install MacOS Mojave on the MacOS partition just created.
11. In MacOS, use Bootcamp to install Windows on the other partition.
12. Once installed and booted in the Windows, you'll see that the WinMac HDD doesn't show up in File Explorer. To fix this, open Disk Management and select the WinMac HDD, right click and Change Drive Letter and Paths..
13. All done! Enjoy!

Hope you guys find this useful!

Thanks,

Krishna