VM using too much RAM from NFS share (ZFS)

[Alanl96]

Hi everyone, I am hurting for memory at the moment and I need a temporary fix until my Epyc parts arrive in December. I posted a question regarding ZFS memory usage and you guys pointed me to the right place to change how much memory the host system uses for ZFS. I have that ZFS volume shared to my Plex VM using an NFS share. My VM won't change, I changed the host to 40GB (a really bad idea) and rebooted the VM. The VM is still consuming 64ish GB of memory (I don't actually know because the VM is set for 64GB of RAM and it's red lining). How do you decrease the memory utilization of VMs with ZFS NFS share? I have eight 8TB HDDs in RAID 10 with compression enabled, and I think you need 1GB of RAM for every 1TB of raw storage in ZFS. That puts me at 64GB for the host and 64GB to each VM using my ZFS volume. I had no idea that the memory consumption problem would be passed on to my VMs. I figured that out really fast after I installed Proxmox.

 

[leesteken]

If you want a VM to use less memory, you could just set it to less memory.
The memory usage graph having a red color is not a problem in and of itself.
Did you install the QEMU Guest Agent inside the VM and enable it in the VM Options? This will hide the filesystem cache from the graph.

 

[Alanl96]

No, I didn't install QEMU Guest Agent. I am so new to this hypervisor as a primary OS thing. Thanks for your help!

 

[Dunuin]

Did you install the QEMU Guest Agent inside the VM and enable it in the VM Options? This will hide the filesystem cache from the graph.

At least here that is only true for Windows VMs. Not for Linux or FreeBSD. But the QEMU Guest Agent should be installed anyway, because otherwise backups/snapshots won't do a fsfreeze so no guaranteed data integrity as caches won't be flushed first.

 

[leesteken]

At least here that is only true for Windows VMs. Not for Linux or FreeBSD.

Thank you for pointing this out. If someone with a Linux VM panics about a red graph, they'll just have to read Linux ate my ram,

 

[Alanl96]

Thank you for pointing this out. If someone with a Linux VM panics about a red graph, they'll just have to read Linux ate my ram,

Thanks for the help. I can't believe I have been using Ubuntu server for a year and I haven't noticed RAM caching. I was using 100GB of memory for all of my services. Unless cockpit doesn't report RAM caching... ZFS took the 64GB of RAM as expected, Minecraft took 12 GB. I probably bought too much RAM for this Epyc build. I bought 512GB.