Apps with 'I/O Monitoring' feature
An application which manages kernel parameters.
It depends on your kernel which features you can use.
A collection of performance monitoring tools (of which iostat and sar for I/O, CPU, memory and more ) for GNU/Linux OS. Let you monitore ponctually by hand as well as automatically via cron or systemd services.
The Bubbling Load Monitor (or "Bubblemon" for short) is a system CPU and memory load monitor. It displays something that looks like a vial containing water.