sudo diskinfo -t /dev/mirror/gm0
        512             # sectorsize
        320072932864    # mediasize in bytes (298G)
        625142447       # mediasize in sectors

Seek times:
        Full stroke:      250 iter in   1.605701 sec =    6.423 msec
        Half stroke:      250 iter in   1.564172 sec =    6.257 msec
        Quarter stroke:   500 iter in   3.201909 sec =    6.404 msec
        Short forward:    400 iter in   2.648792 sec =    6.622 msec
        Short backward:   400 iter in   2.597294 sec =    6.493 msec
        Seq outer:       2048 iter in   0.159986 sec =    0.078 msec
        Seq inner:       2048 iter in   0.169422 sec =    0.083 msec
Transfer rates:
        outside:       102400 kbytes in   1.420254 sec =    72100 kbytes/sec
        middle:        102400 kbytes in   1.608271 sec =    63671 kbytes/sec
        inside:        102400 kbytes in   2.975405 sec =    34415 kbytes/sec