err = readDirFn(baseDir, func(name string, typ os.FileMode) error {
		if !typ.IsDir() {
			return nil
		}
		// See if directory has a UUID name.
		base := filepath.Base(name)
		_, err := uuid.Parse(base)
		if err == nil {
			foundDirs[base] = struct{}{}
		}
		return nil
	})
	if err != nil {
		return err
	}
	wantDirs, err := xl.getDataDirs()
	if err != nil {
		return err