problem

Restore fails silently if the data volume was created before the root volume and backup was taken using the NAS backup provider.

versions

ACS 4.20

The steps to reproduce the bug

1. Create a data volume V1
2. Create an instance Instance1
3. Attach V1 to Instance1
4. Write a file test.txt into Instance1's root disk.
5. Create backup B1 of Instance1
6. Stop Instance1 and restore B1
7. Restore finishes in a few seconds without any error.
8. The file test.txt is absent from Instance1

What to do about it?

Restore should succeed.
At the least it should throw error if data is not restored.