Host memory usage

Jun 28, 2019

My proxmox 6.0 host is reporting 56GB of RAM usage, but the sum of my total VMs (5) running is only 15GB (considering the total memory allocation, not used memory on guest), this host does not run CEPH or any other services, just KVM process, what is consuming so much memory if the sum of my VMs (5 in total) is only 15GB ?

All running guests have the same hardware config, 4 are windows 2016, 1 is Debian system:

MEMORY : 1.5GB min, 3,0 GB max

Attached is the screenshots..


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  • gues-memory-allocation.PNG
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It appears that some local filesystem is doing a lot of cache, (maybe ZFS) ?

I executed:
echo 3 > /proc/sys/vm/drop_caches

Host memory lowered to 20GB...
I confirmed that ZFS ARC cache is consuming this memory...

Running the command below, shows ZFS arc cache using almost 35GB...

awk '/^size/ { print $1 " " $3 / 1048576 }' < /proc/spl/kstat/zfs/arcstats

So, I have three questions:

1- There is any way to limit this ARC cache on ZFS-local proxmox setup ?

2 - Limiting the ARC cache can result in any side effect in terms of performance?

3 - If the KVM guest require this cached memory, will ZFS release it for other applications?

thanks in advance


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