High memory usage without any VM's Running

JaK

New Member
May 22, 2021
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Hello there!
Recent changes:
i have recently migrated my boot device on my proxmox server to two Seagate Iron Wolf M.2 SSD's - which are running in a raid1 configuration for failover.
After setting up proxmox i started migrating all my VM's to it, thats where i noticed something weird. Proxmox seemed to be using a lot more ram than it used to.
About an hour into the migration i noticed that some vm's - in perticular the TrueNAS VM - were Kernel panicking because of insufficient RAM/Swap.
What i tried:
I just thought, maybe the guests were expecting some SWAP from my hypervisor. So i gave it 4 more GB's SWAP storage. This did indeed result in less kernel panicks from my guests, but the high memory usage was still present. (This did not really sove the issue, but it just meant, that i had more ram essentially)
After disabling and enabling ballooning on different VM's i concluded to just shut all down and see what happens, this is what i observed: (I had to censor the names of the vm's because they also contain my location :) )
1621679943986.png
This image was taken about 15 minutes after all VM's had been shut down.

This is what HTOP showed: (sorted by memory)
1621680125683.png

Why is proxmox using 16 GB's of ram for no apparent reason? Is this issue known/did i configure something wrong? (I don't know what configs could be relevant for this, so please just ask ;) )

Thanks in advance
Jack
 
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Just a note:
This is NOT immediately apparent when restarting proxmox, but rather after about an hour.
All vm's are running Debian except for one TrueNAS and one Windows 10 Professional x64 (Also using the guest agent and balloon drivers, i have tested why any configuration of these, it does not seem to make a difference)
 
If you use raid1 you are most likely using ZFS and ZFS is using 50% of your RAM for its ARC for caching. So its totally normal that you loose 16GB RAM. Look here how to reduce the ARC size.
 
If you use raid1 you are most likely using ZFS and ZFS is using 50% of your RAM for its ARC for caching. So its totally normal that you loose 16GB RAM. Look here how to reduce the ARC size.
Hello Dunuin,
this worked like a charm! Thank you very much!

Best regards
Jack
 
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