7. Using Monitoring and Tracing Tools : Operating System Utilities : UNIX Operating System Utilities : iostat
 
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iostat
The iostat command returns information about I/O status. It lists statistics on current I/O activity for each disk device and system CPU utilization percentages. Here is a sample iostat output:
tty cpu
tin    tout    us    ni    sy    id
  1      18    19     0     3    78 
/dev/*dsk/c0d*s*/dev/*dsk/cld*s*/dev/*dsk/c2d*s*/dev/*dsk/c4d*s*
bps   sps   msps  bps   sps   msps   bps   sps   msps   bps   sps   msps
 2    0.1   61.7   1    0.0   95.5    1    0.0   60.4    2    0.2   44.3
The tin and tout display fields show the number of characters written to and from terminal devices.
CPU information includes the % time spent in user mode (us), “niced” user mode (ni), system mode (sy), and idle (id).
The disk I/O for each disk device shows the average number of blocks transferred per second (bps), average number of seeks per second (sps), and average time per seek in ms (msps).