Comment # 16 on bug 1205374 from Stefan Hundhammer

Some values are cached from a prior storage hardware probing because that
probing is a time-consuming thing, and some of the external commands that it
issues may even hang (in some pathological scenarios).

If you modify any partitioning or storage hardware outside of YaST, you may
have to trigger that probing again: In the partitioner, select "Rescan Devices"
from the "System" menu on the top left.

Failing that, after you wrote your changes to disk (which most command line
utilities implicitly do, or "fdisk" when you prompt it to), simply rebooting
from the installlation media again is another option.