Kernel errors drive_cmd

How serious are these errors?

Code:

 WARNING:  Kernel Errors Present
    hda: drive_cmd: error=0x04 { DriveStat ...:  2 Time(s)
    hda: drive_cmd: status=0x51 { DriveReady SeekComplete Error } ...:  2 Time(s)
    hdd: drive_cmd: error=0x04 { DriveStat ...:  2 Time(s)
    hdd: drive_cmd: status=0x51 { DriveReady SeekComplete Error } ...:  2 Time(s)

Code:

 --------------------- Smartd Begin ------------------------ 

 
 /dev/hdd :
    Prefailure: Seek_Time_Performance (8) changed to 
      243, 244, 243, 244, 243, 244, 
 
 /dev/hda :
    Failed usage attribute: Power_On_Seconds (9) 48 Time(s)

 

Not good. It seems your hard drives are dying...