I recently had a Proxmox server with limited amount of RAM (32Gb) that would randomly have VMs turn off. Now while ZFS should (and does) release RAM for other apps and services there is a bit of a delay in doing so causing the server to run out of resources and turn the VMs off.
ZFS will use up to 50% of installed RAM by default so as a workaround I could safely limit the ARC Max Size to 4Gb [4*1024*1024*1024] without too much of a performance impact on the VMs or server but still keeps the VMs running
to do this I ran the following commands on the server
The first command will set the max RAM without having to reboot the server and the second command makes the changes survive reboots
echo "options zfs zfs_arc_max=4294967296" >>/etc/modprobe.d/zfs.conf
echo "4294967296" >>/sys/module/zfs/parameters/zfs_arc_max
