From: http://sourceware.org/systemtap/wiki/WSiostatSCSI

# stap -g iostat-scsi.stp 10 # seconds between reports
  Device:       tps blk_read/s blk_wrtn/s  blk_read  blk_wrtn
      sda      1.30      2.40    105.60        24      1056

      sda      0.30      0.00      4.00         0        40

      sda     21.30      1.60    428.80        16      4288

      sda     30.40   2820.80     11.60     28208       116

      sda     38.10   2816.80     53.60     28168       536
^C
