The software described in this documentation is either in Extended Support or Sustaining Support. See https://www.oracle.com/us/support/library/enterprise-linux-support-policies-069172.pdf for more information.
Oracle recommends that you upgrade the software described by this documentation as soon as possible.
The iostat command monitors the loading of block I/O devices by observing the time that the devices are active relative to the average data transfer rates. You can use this information to adjust the system configuration to balance the I/O loading across disks and host adapters.
iostat -x reports extended statistics about
block I/O activity at one second intervals, including
%util, which is the percentage of CPU time
spent handling I/O requests to a device, and
avgqu-sz, which is the average queue length
of I/O requests that were issued to that device. If
%util approaches 100% or
avgqu-sz is greater than 1, device
saturation is occurring.
You can also use the sar -d command to
report on block I/O activity, including values for
%util and avgqu-sz.
The iotop utility can help you identify
which processes are responsible for excessive disk I/O.
iotop has a similar user interface to
top. In its upper section,
iotop displays the total disk input and
output usage in bytes per second. In its lower section,
iotop displays I/O information for each
process, including disk input output usage in bytes per
second, the percentage of time spent swapping in pages from
disk or waiting on I/O, and the command name. Use the left and
right arrow keys to change the sort field, and press
A to toggle the I/O units between bytes per
second and total number of bytes, or O to
toggle between displaying all processes or only those
processes that are performing I/O.