- Solved
- Minor
I've been having this issue for the past while and finally making a post on it. This is what I am doing and this is what I observe:
-
There will be cases when Unraid is low on free memory such as
- spinning up a VM
- copying a lot of files from VM to host via SFTP which caches files in RAM
- Docker containers temporarily needing to use a lot of RAM for certain operations
-
In these cases, when Unraid reaches this "close to out of memory" scenario, it will:
- Cause significant read activity on the USB with significant IOWait as a symptom
- If I can use the shell, I can see on inotifywait that bzfirmware is being accessed
- The UI is generally inaccessible during this time, nor any of the docker containers.
- Even the User Scripts plugin cannot trigger my 1-min interval cronjob that pushes to an Uptime Kuma instance
-
If I can use the shell, manually dropping caches by the below command resolves the issue
echo 3 > /proc/sys/vm/drop_caches
Below is the read bandwidth of my boot USB during one of these scenarios, averaging around 8 MB/s.
So it seems like instead of caches being evicted from RAM, the OS is being evicted (disclaimer I'm no Linux expert). I have also attached diagnostics below.
Thanks!