Cloudron v9: huge disk I/O is this normal/safe/needed?

[robi]

@imc67 Holding that limiting belief is keeping your problem unresolved, no?

Sure, then trace it from the MySQL side, find which user, which container and so on..

Yes, it has everything to do with the Apps that are using that DB instance.

[james]

Hello @imc67
You can use the PID from the process to figure out what mysql service it is.

e.g. your iotop shows for mysqld the pid 1994756.
You can run systemctl status mysql.service and there is the pid displayed:

● mysql.service - MySQL Community Server
     Loaded: loaded (/usr/lib/systemd/system/mysql.service; enabled; preset: enabled)
     Active: active (running) since Mon 2025-12-01 09:17:59 UTC; 1 week 5 days ago
   Main PID: 1994756 (mysqld)
     Status: "Server is operational"
      Tasks: 48 (limit: 4603)
     Memory: 178.7M (peak: 298.0M swap: 95.4M swap peak: 108.7M)
        CPU: 1h 41min 31.520s
     CGroup: /system.slice/mysql.service
             └─1994756 /usr/sbin/mysqld

Notice: journal has been rotated since unit was started, output may be incomplete.

So from iotop I can confirm that the system mysqld service is pid 1994756 so I'd know to inspect the system mysqld service and not the docker mysql service.

You can also get the pid from the mysqld inside the docker container with docker top mysql:

docker top mysql
UID                 PID                 PPID                C                   STIME               TTY                 TIME                CMD
root                1889                1512                0                   Nov07               ?                   00:06:17            /usr/bin/python3 /usr/bin/supervisord --configuration /etc/supervisor/supervisord.conf --nodaemon -i Mysql
usbmux              3079                1889                0                   Nov07               ?                   03:49:38            /usr/sbin/mysqld
usbmux              3099                1889                0                   Nov07               ?                   00:00:11            node /app/code/service.js

Then I know the mysqld pid of the docker service is 3079 which I can check again with the system:

ps uax | grep -i 3079
usbmux      3079  0.4  1.0 1587720 43692 ?       Sl   Nov07 229:38 /usr/sbin/mysqld

Now we can differentiate between the two.

---

Okay.
Now that we can differentiate between the two, you can observe iotop and see which one has a high I/O.
After you narrow it down to either one, then we can do some analysis what database / table get accesses the most even further narrow it down.