[root@localhost opt]# hdparm -Tt /dev/sda

/dev/sda:
 Timing cached reads:   4402 MB in  2.00 seconds = 2203.47 MB/sec
 Timing buffered disk reads:  118 MB in  3.03 seconds =  38.93 MB/sec
[root@localhost opt]# hdparm -cd /dev/sda

/dev/sda:
[root@localhost opt]# hdparm -I /dev/sd
sda   sda1  sda2  sda3  sda5  
[root@localhost opt]# hdparm -I /dev/sda

/dev/sda:
 HDIO_DRIVE_CMD(identify) failed: Invalid argument