[CentOS] Disk read io very high, but no process perform io read

Fri Mar 5 15:03:51 UTC 2021
Joshua Kramer <joskra42.list at gmail.com>

Install a program called iotop.  iotop will show you, in real time,
which processes are using the most i/o bandwidth.

On Fri, Mar 5, 2021 at 2:54 AM yf chu <cyflhn at 163.com> wrote:
> We have experienced a very weird problem. The load of the server machine is very high. We use "pidstat" and find that the disk read io is very high.
> But the processes running on this server do not perform any disk read operation.
> We also noticed that when we execute "top" command, for most of processes, the values in "SHR" column are zero.
> Compared with other normal servers, we found that by executing "free -m", the result shows that the buff/cache value in this server is lower than the value of other normal servers.
> We also found that there were lots of major page faults by executing "ps -o majflt,minflt".
> Swap is not enabled on this server. What could be the reason for this issue?
> The centos version:CentOS Linux release 7.3.1611
> kernel version:3.10.0-693.21.1.std7a.el7.0.x86_64
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