Linux server administration/sar/sar -d

sar -d To report disk (block devices) activity. See also iostat -x.

sar -d
02:45:01 PM       DEV       tps     rkB/s     wkB/s   areq-sz    aqu-sz     await     svctm     %util
02:46:01 PM    dev7-0      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
02:46:01 PM    dev7-1      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
02:46:01 PM    dev7-2      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00

%iowait column from sar command also provide information about disk I/O requests.

sar
01:12:01 PM     CPU     %user     %nice   %system   %iowait    %steal     %idle
01:13:01 PM     all      2.99      0.00      6.58      7.13      0.00     83.30
01:14:01 PM     all      5.39      0.00      2.30      6.70      0.00     85.61
01:15:01 PM     all      4.80      0.00      0.96      8.91      0.00     85.33
01:16:01 PM     all      4.65      0.00      0.64      6.19      0.00     88.52