I/O Monitoring #
Lesson Content #
We can also monitor CPU usage as well as monitor disk usage with a handy tool known as iostat
pete@icebox:~$ iostat
Linux 3.13.0-39-lowlatency (icebox) 01/28/2016 _i686_ (1 CPU)
avg-cpu: %user %nice %system %iowait %steal %idle
0.13 0.03 0.50 0.01 0.00 99.33
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 0.17 3.49 1.92 385106 212417
The first part is the CPU information:
- %user - Show the percentage of CPU utilization that occurred while executing at the user level (application)
- %nice - Show the percentage of CPU utilization that occurred while executing at the user level with nice priority.user CPU utilization with nice priorities
- %system - Show the percentage of CPU utilization that occurred while executing at the system level (kernel).
- %iowait - Show the percentage of time that the CPU or CPUs were idle during which the system had an outstanding disk I/O request.
- %steal - Show the percentage of time spent in involuntary wait by the virtual CPU or CPUs while the hypervisor was servicing another virtual processor.
- %idle - Show the percentage of time that the CPU or CPUs were idle and the system did not have an outstanding disk I/O request.
The second part is the disk utilization:
- tps - Indicate the number of transfers per second that were issued to the device. A transfer is an I/O request to the device. Multiple logical requests can be combined into a single I/O request to the device. A transfer is of indeterminate size.
- kB_read/s - Indicate the amount of data read from the device expressed in kilobytes per second.
- kB_wrtn/s - Indicate the amount of data written to the device expressed in kilobytes per second.
- kB_read - The total number of kilobytes read.
- kB_wrtn - The total number of kilobytes written.
Exercise #
Use iostat to view your disk usage.
Quiz Question #
What command can be used to view I/O and CPU usage?
Quiz Answer #
iostat