// 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)

		format := &formatErasureV3{}
		json := jsoniter.ConfigCompatibleWithStandardLibrary
		if err = json.Unmarshal(s.formatData, &format); err != nil {
			return s, errCorruptedFormat
		}
		m, n, err := findDiskIndexByDiskID(format, format.Erasure.This)
		if err != nil {
			return s, err
		}
		diskID := format.Erasure.This
		if m != ep.SetIdx || n != ep.DiskIdx {
			storageLogOnceIf(context.Background(),