federico@cybertron:~$ sudo hdparm -tT /dev/sdb
/dev/sdb:
 Timing cached reads:   25662 MB in  1.99 seconds = 12879.79 MB/sec
 Timing buffered disk reads: 1306 MB in  3.00 seconds = 434.77 MB/sec
federico@cybertron:~$ sudo hdparm -W /dev/sdb
/dev/sdb:
 write-caching =  1 (on)
federico@cybertron:~$ sudo hdparm -W 0 /dev/sdb
/dev/sdb:
 write-caching =  0 (off)
federico@cybertron:~$ sudo hdparm -tT /dev/sdb
/dev/sdb:
 Timing cached reads:   25252 MB in  1.99 seconds = 12672.90 MB/sec
 Timing buffered disk reads: 1080 MB in  3.00 seconds = 359.86 MB/sec
federico@cybertron:~$