How to Monitor Linux Systems Performance with iostat command

Linux-iostat-command

iostat command is used to monitor CPU utilization and I/O (input /output) statistics of all the disks and file systems. nfsiostat command is used to monitor i/o statistics of network file system(NFS).

iostat command monitor the I/O (Input/Output) devices loading by means of observing the time, devices are active with respect to their average transfer rates. This command is especially helpful for generating reports that we can use to optimize the system’s input & output load.

iostat command generally generates two reports:

  • CPU utilization report
  • All disks i/o statistics report

To generate the reports, iostat command reads some of the system files . These files are,

  • /proc/diskstats for disk stats
  • /proc/stat for system stats
  • /sys for block device stats
  • /proc/devices for persistent device names
  • /proc/self/mountstats for all  the network filesystems
  • /proc/uptime for information regarding system uptime

In this tutorial, we will learn how to install iostat utility on Linux systems and then we will discuss how to generate reports using iostat command,

Iostat Installation on Linux Systems:

iostat is a part of ‘sysstat‘ package, we can install it on our system using the following command,

CentOS/RedHat

[[email protected] ~]# yum install sysstat -y

Ubuntu/Debian

$ sudo apt-get install sysstat -y

Fedora

[[email protected] ~]# dnf install sysstat -y

Now let’s check out some examples to understand the iostat command better.

Example:1 Get complete statistics (CPU & Devices)

To get the complete statistics for the system, open terminal & execute the following command,

[[email protected] ~]# iostat

This will produce the following output on the screen,

iostat-command-output

Here in the iostat command output,

  • %user, is CPU utilization for the user,
  • %nice, is the CPU utilization for apps with nice priority,
  • %system, is the CPU being utilized by the system,
  • %iowait, is the time percentage during which CPU was idle but there was an outstanding i/o request,
  • %steal, percentage of time CPU was waiting as the hypervisor was working on another CPU,
  • %idle, is the percentage of time system was idle with no outstanding request.

Devices, shows the name of all the devices on system,

  • Tps, is the short for transfer per second,
  • Blk_read/s & Blk_write/s are the transfer speed for read and write operations,
  • Blk_read & Blk_write shows the total number of blocks read & written.

Example:2 Generate only CPU stats

To only generate the CPU statistics for the system, we will use options ‘c’ with iostat. Run the following command from terminal,

[[email protected] ~]# iostat -c

iostat-cpu-utilization

Example:3 To Generate i/o statistics for all the devices (-d option) 

To get the iostat report only for the devices connected on the system, we will use option ‘d’ with iostat command,

[[email protected] ~]# iostat -d

device-statistics-iostat-command

Example:4 Generate detailed i/o statistics

Though usually the stats provide by iostat command are sufficient but if you wish to get even more detailed statistics, we can use ‘-x’ option along with iostat command. Example is shown below,

[[email protected] ~]# iostat -x

Detailed-io-statistics-iostat-command

Example:5 Generate detailed reports for devices & CPU separately

To get the detailed information regarding the devices on the system, we will use option ‘d’ along with option ‘x’,

[[email protected] ~]# iostat -xd

Detailed-stats-disk-only-iostat-command

Similarly, for generating the detailed information for CPU, we will use options ‘c’ & ‘x’,

[[email protected] ~]# iostat -xc

Example:6 Getting i/o statistics for a single device

iostat can also provide the i/o statistics for a single device. To get the statistics of a device, execute iostat command along with option ‘p’ followed by device name,

[[email protected] ~]# iostat -p sda

io-statistics-single-device-iostat-command

Example:7 Generate reports in either MB or KB

We can also generate the system statistics in either Megabytes or kilobytes units. To generate the reports in mb, we will use option ‘m’ with iostat command,

[[email protected] ~]# iostat -m

iostat-report-mb

Similarly, we can also generate the reports in kb unit format with option ‘k’,

[[email protected] ~]# iostat -k

Example:8 Generating system i/o statistics report with delay

To capture the system statistics with a delay, we can mention the iostat command followed by interval in seconds & number of reports required,

[[email protected] ~]# iostat 3 2

In this example, we are capturing 2 reports at 3 seconds interval,

iostat-reports-delay

We can also use the delay parameter along with other options of iostat command that we discussed above.

Example:9 Generate the LVM statistics report

To generate the LVM statistics, we can use option ‘N’ with iostat command,

[[email protected] ~]# iostat -N

LVM-statistics-iostat-command

Example:10 Generate the reports for only active devices

We can also generate reports for devices that are active & omit out devices from reports that are inactive for sample period. We will use option ‘z’ with iostat command to accomplish this,

[[email protected] ~]# iostat -z 2 5

iostat-reports-active-device-delay

Example:11 Generate iostat reports with timestamp

To generate the iostat reports with a timestamp, we will use option ‘t’ along with iostat command,

[[email protected] ~]# iostat -t

iostat-report-timestamp

Example:12 Generate statistics report based on persistent device name

To get the report based on the persistent name of the device, we will use the option ‘j’ followed by keyword ‘ID’ & device persistent name,

Use blkid command to find the UUID of the disk.

blkid-command-output

Once you find the UUID / ID then use the below iostat command,

[[email protected] ~]# iostat -j id 12244367-e751-4c1c-9336-f30d623fceb8

iostat-id-command-output

Example:13 Generate i/o statistics for Network File System(NFS)

We can use nfsiostat command to generate the NFS i/o statistics reports. nfsiostat command is the part of the package ‘nfs-utils’. Let’s assume we have mounted two NFS shares on our server, so to generate the statistics report for NFS share run the below command,

[[email protected] ~]# nfsiostat

nfsiostat-command-output

Example:14 Generate System I/O statistics report over a period of time

iostat command generate the live i/o statistics of your system and if you want to view the statistics reports over a period of time (back date system i/o statistics) then we should use sar utility. Sar command is also provided by the package ‘sysstat’

Read More on “Generate CPU, Memory and I/O report using SAR command

That’s it guys, we have covered all the options/parameters that can be used with iostat command. You can try mixing these options to get more desired/detailed results. Please do mention any query or question that you have regarding the tutorial.

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