// For any unexpected error, return checkPartUnknown (zero)
func (s *xlStorage) checkPart(volumeDir, path, dataDir string, partNum int, expectedSize int64, skipAccessCheck bool) (resp int) {
	partPath := pathJoin(path, dataDir, fmt.Sprintf("part.%d", partNum))
	filePath := pathJoin(volumeDir, partPath)
	st, err := Lstat(filePath)
	if err != nil {
		if osIsNotExist(err) {
			if !skipAccessCheck {