Hm, I seem to be able to override this as a daemon opt:
.\dockerd.exe --storage-opt size=30G
docker run --storage-opt size=30G microsoft/nanoserver powershell -c get-psdrive
Name Used (GB) Free (GB) Provider Root
---- --------- --------- -------- ----
Alias Alias
C 0.16 29.72 FileSystem C:\
Here’s how to make that permanent:
net stop docker
.\dockerd --unregister-service
.\dockerd --register-service -storage-opt size=30G
net start docker
Let me know if that doesn’t work.