Can dual redundancy help with a disk failure during a rebuild?

When a drive fails, replacing it with a good disk triggers a rebuild process. I believe during the rebuild, any single disk failure will cause all data to be lost. With dual redundancy, I’m hoping that a single-disk failure during a rebuild will not result in total data lost. Can someone confirm the validity of these statements?

I would love too see this demo on a Drobo S with dual redundancy:

  1. remove a disk.
  2. replace disk with a blank one. rebuild should start.
  3. while rebuild is still in progress, remove another disk (not the blank one). check if data can still be accessed.

yes, your data is safe in that instance, that is the point of dual disk redundancy - you can survive a second disk failure during the rebuild from a single disk failure