Zram 100% full a few minutes after start of openHab

Setup, Configuration and Use Installation
1

I am running openHab on my Raspberry Pi 4.

This is the output after a few minutes of openHab running on it:

openhabian@openhabian:~ $ zramctl --output-all
NAME       DISKSIZE   DATA COMPR ALGORITHM STREAMS ZERO-PAGES TOTAL MEM-LIMIT MEM-USED MIGRATED MOUNTPOINT
/dev/zram0       1G     4K    4K lzo-rle         4          0    4K      500M       4K       0B [SWAP]
/dev/zram1     750M 504.1M  500M zstd            4       1061  500M      500M     500M       0B /opt/zram/zram1
/dev/zram2       1G   100M 72.6M zstd            4       7017 72.6M      600M    72.6M       0B /opt/zram/zram2

Besides openHab there is zigbee2mqtt running on it aswell. Installed from then openhabian-config menu.

What could cause this?
What can I do to fix it?

2

what does

df -h

tell you ?

3

This is the output of df -h

openhabian@openhabian:~ $ df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            3.6G     0  3.6G   0% /dev
tmpfs           790M  2.1M  788M   1% /run
/dev/mmcblk0p2   59G  7.9G   48G  15% /
tmpfs           3.9G     0  3.9G   0% /dev/shm
tmpfs           5.0M   16K  5.0M   1% /run/lock
/dev/mmcblk0p1  510M   96M  415M  19% /boot/firmware
/dev/zram1      721M  488M  182M  73% /opt/zram/zram1
overlay1        721M  488M  182M  73% /var/lib/openhab/persistence
/dev/zram2      974M   41M  866M   5% /opt/zram/zram2
overlay2        974M   41M  866M   5% /var/log
tmpfs           790M     0  790M   0% /run/user/1000
4

zram1 is where persistence is stored, seems you have an unusual amount of data put there and update
regularly so it stays in (Z)RAM, did you install some DB there like Influx ?
If you have enough RAM you can increase in /etc/ztab but in general that’s a bad idea to combine hence not recommended as also say the docs.

5

I had rrd4j persistence installed but uninstalled it yesterday. No other persistence binding is installed.

When rrd4j was still installed I got Read only file system errors after a while. I assume because the zram was full.

Also switched to a completely new SD card before making this thread to rule out the possibility of a faulty/degraded SD card.

Could this zram issue also cause the Alexa integration to not work correctly anymore? No new devices get detected by Alexa even though everything is tagged correctly.

Edit:

I just restarted openhab and till 5 minutes it does not seem to fill up anymore.

So I assume that the rrd4j persistence was filling up the zram (but I don’t know what could cause this immense amount of data).

The issue that still remains is that the Alexa integration seems not to work correctly anymore