// format, after successful validation.
//   - i'th position is the set index
//   - j'th position is the disk index in the current set
func findDiskIndexByDiskID(refFormat *formatErasureV3, diskID string) (int, int, error) {
	if diskID == "" {
		return -1, -1, errDiskNotFound
	}
	if diskID == offlineDiskUUID {
		return -1, -1, fmt.Errorf("DriveID: %s is offline", diskID)