When dealing with a server experiencing slowness, you may wish to determine if there is high I/O on the server using the "iostat" process.
By running the following command, you will see the system resource usage that relates to CPU usage and disk I/O Wait times:
(Note: this command does not work on OpenVZ/Virtuozzo containers)
# iostat
Linux 3.10.0-1127.el7.x86_64 (cptest.cptest-2.com) 05/17/2020 _x86_64_ (1 CPU)
avg-cpu: %user %nice %system %iowait %steal %idle
0.85 0.10 0.74 0.15 0.03 98.13
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
vda 3.18 146.58 13.32 237730042 21596664
vdb 0.00 0.00 0.00 6554 0
The column "%iowait" is the percentage of time it takes for CPU to complete a task.
Though some IO-wait time is normal, the higher the value, the more time it takes to complete tasks, increasing slowness across the entire server.
Definition: IO-wait : time waiting for I/O completion
The command 'iostat' will give you an overview of total server disk I/O usage. You can reference it in a couple of ways.
The first command will print the disk usage statistics ten times, every 1 second. Check the %util column:
Realtime disk I/O usage
[user@host ~]$ iostat -x 1 10
The next command can show I/O values from the SAR logs:
Historial disk I/O usage
[user@host ~]$ sar -d
The 'iostat' command can help with a broad overview of a high load issue on a server-wide basis. To help locate any processes that may be contributing, you may wish to check the process list on the server:
The 'iotop' command is useful for gathering information regarding disk usage:
For additional assistance, you may wish to contact your System Administrator or hire a qualified System Administrator.
You can find qualified System Administrators for hire on our website here:
https://forums.cpanel.net/resources/categories/system-administration-services.1/
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