VmWare Disk：I/O command overhead:

time to read 10MB block 0.378316 sec = 0.018 msec/sector
time to read 20480 sectors 8.416036 sec = 0.411 msec/sector
calculated command overhead = 0.392 msec/sector

9.1G SCSI：I/O command overhead:

time to read 10MB block 0.744310 sec = 0.036 msec/sector
time to read 20480 sectors 9.478580 sec = 0.463 msec/sector
calculated command overhead = 0.426 msec/sector

160G SATA：I/O command overhead:

time to read 10MB block      0.199352 sec       =    0.010 msec/sector
time to read 20480 sectors   1.586855 sec       =    0.077 msec/sector
calculated command overhead                     =    0.068 msec/sector