dom0:

box0:~# hdparm -Tt /dev/sda

/dev/sda:
 Timing cached reads:   1860 MB in  2.00 seconds =thulium:~# hdparm -Tt /dev/sda

/dev/sda:
 Timing cached reads:   1860 MB in  2.00 seconds = 929.89 MB/sec
 Timing buffered disk reads:  202 MB in  3.01 seconds =  67.12 MB/sec
 929.89 MB/sec
 Timing buffered disk reads:  202 MB in  3.01 seconds =  67.12 MB/sec

domU:

boxU1:/home/otto# hdparm -Tt /dev/sda1

/dev/sda1:
 Timing cached reads:   1780 MB in  2.00 seconds = 889.65 MB/sec
 Timing buffered disk reads:  168 MB in  3.02 seconds =  55.62 MB/sec