for index := range disks {
		g.Go(func() error {
			if disks[index] == nil {
				return errDiskNotFound
			}

			// Pick one FileInfo for a disk at index.
			fi := metadata[index]
			// Assign index when index is initialized
			if fi.Erasure.Index == 0 {
				fi.Erasure.Index = index + 1
			}

			if !fi.IsValid() {
				return errFileCorrupt
			}