硬盘为三星850 EVO 250GB

SATA3 - 6 Gbps

$ sudo hdparm -t /dev/sda
/dev/sda:
 Timing buffered disk reads: 1320 MB in  3.00 seconds = 439.57 MB/sec

$ sudo hdparm -t /dev/sda
/dev/sda:
 Timing buffered disk reads: 1362 MB in  3.00 seconds = 453.66 MB/sec

$ sudo hdparm -T /dev/sda
/dev/sda:
 Timing cached reads:   13440 MB in  2.00 seconds = 6725.97 MB/sec

$ sudo hdparm -T /dev/sda
/dev/sda:
 Timing cached reads:   13470 MB in  2.00 seconds = 6740.97 MB/sec

USB 3.0 - 5 Gbps

$ sudo hdparm -t /dev/sda
/dev/sda:
 Timing buffered disk reads: 1320 MB in  3.00 seconds = 332.65 MB/sec

$ sudo hdparm -T /dev/sda

/dev/sda:
 Timing cached reads:   13440 MB in  2.00 seconds = 5675.85 MB/sec