Hey @rajendar erabathini ,
There are 2 aspects:
- Powerbi can connect to Cube via import mode as well wherein the data would reside in powerBi service.
But in case if the mode is connect Live and the cube refresh fails, the cube still has stale/legacy data.
So the PowerBi report would still be showing data but the legacy ones
Also, even though SQL DW doesn't allow all features similar to SQL, you an control and validate the data before ingesting into SQL DW,
There are also tools like Great Expectations that help in data quality testing.
2) Why do you want 2 copies of cube ? Because irrespective of whether the cube is getting processed or not , the reporting cube would either show latest data or legacy one.
So there is no use of having 2 cubes as both would serve the same purpose as 1 cube itself but with additional maintenance .