I finally found a solution to this problem. As someone already said in this thread, Windows 10 build 1809 doesn't allow to have the paging file on "portable drives" anymore. So if you click on the "Safely Remove Hardware and Eject Media" icon in the system tray and you see the drive that you want to use for the page file there, then Windows will refuse to use it. The problem is that the BIOS on some older motherboards seems to report the internal SATA ports as "external" ports to Windows. There are now two solutions:
- Deactivate this behavior for the SATA ports in the BIOS (it should be called "hot-swappable", "non-removable" or something like this). However, this seems to only be available on newer mainboards.
- Tell Windows that the SATA ports are non-removable.
I had to use the second solution. Here you can find a nice guide:
https://superuser.com/a/961242
I'm not sure how to get the number of a specific SATA port, I also used 0 to 5. Maybe it's the SCSI bus under win+r, msinfo32, System Summary, Components, Storage?
I hope this helps.