private function hdd_write_speed_linux()
 {
     if ($this->disk_to_monitor == NULL) {
         return -1;
     }
     $stat_path = '/sys/class/block/' . $this->disk_to_monitor . '/stat';
     $speed = phodevi_linux_parser::read_sys_disk_speed($stat_path, 'WRITE');
     return $speed;
 }
 public static function read_sensor()
 {
     // speed in MB/s
     $speed = -1;
     if (phodevi::is_linux()) {
         static $sys_disk = null;
         if ($sys_disk == null) {
             foreach (pts_file_io::glob('/sys/class/block/sd*/stat') as $check_disk) {
                 if (pts_file_io::file_get_contents($check_disk) != null) {
                     $sys_disk = $check_disk;
                     break;
                 }
             }
         }
         $speed = phodevi_linux_parser::read_sys_disk_speed($sys_disk, 'READ');
     }
     return $speed;
 }