High load on Raspberry Pi 4 (4GB) since switch to USB boot


i need some hints or help :grin:

I use Openhabian since 2016. I’ve started on a RPI 3b with usb boot and Openhab on a M2-SSD.
About a year ago i’ve upgraded from stretch to buster and switch to a RPI4. Because of missing USB boot support i’ve booted Openhabian from my old SD card (but use the SSD as system disk).

Last week i’ve started to switch to USB boot from my SSD and upgraded the bootloader (with PI Imager) to directly boot from USB. Also updated Openhabian to newest version (with OH 2.5 support) over openhabian-config. OS was already up-to-date because of using unattend-upgrade in Raspbian buster.
It works smooth, no SD card needed anymore.

But: since i’ve boot directly from my SSD the system load has increased about 200%. Before the load was 0.5 on normal state. Since there the system is permanently 1.2-1.5.

If i stop Openhab, Grafana-Server, Influx, Samba and Webmin (using for monitoring) the load don’t decrease under 1.0 - so this ressource consumption should come directly from the operating system.
Here is a screenshot from htop after stopping this services:

I’ve also checked iotop, but no activity on the disk.

Any hints, what could cause this high load or how to debug this?


There’s reasons why openHABian does not support let alone recommend doing what you did to your system: success in this is depending on many factors - way too many to validate and test - and it often just does not work out.
Sorry you took the hard route to find out but as a long time user I’m sure you know the documentation.

I made a mistake in my post, i use Raspbian (default Openhabian install), not Debian. Sorry.

Ok, i think you mean this part of the documentation:

WARNING 2: It will NOT work out of the box to also boot from the USB device. As a Linux or openHAB beginner, you should NOT try this. Using this is NOT recommended to anyone except those to know Linux well enough to manually apply all the required modifications. See [menu option 37].

So i’ll try to solve the hard route and find “all required modifications”. Thanks for the hint.

No. There’s actually hints all over the docs and code.
Actually I mean you should not have done that.
Not in the first place and not now.
The quote sounds like there’s a hidden secret I don’t wanna tell, but that’s far off the real reason which is in fact the one I gave (well it’s one of the major reasons but not the only one).
No matter if you’re proficient in Linux or not .

I switched also from a Pi 3B to 4B and experienced the same.
My load average is always between 0.95 up to about 1.1 since I am booting from an USB SSD.

I googled and found this.
Seems the load average calculation is kind of magic …

I am not a specialist in Linux and my systems is always responsive, no lags or anything else so I do not really care about.
I think the USB or SSD is too slow so the system needs to buffer before writing on disk which increases the “load”.
But I am just guessing.

Sorry if the quote came across that way, that was not my intention.