Memory usage

[Loic92]

Hello,
I have a proxmox node with 32GB of RAM.
I deployed 2 Windows VM, each VM has 8GB of RAM allocated.
But when I'm checking the "Summary" information into the WebUI,
I can see that the memory usage of the node is all the time around 95% of usage!
Can you help to find the explanation?
Thanks.

CPU(s) 12 x Intel(R) Xeon(R) CPU D-1531 @ 2.20GHz (1 Socket)

Kernel Version Linux 5.15.60-2-pve #1 SMP PVE 5.15.60-2 (Tue, 04 Oct 2022 16:52:28 +0200)

PVE Manager Version pve-manager/7.2-11/b76d3178

 

[leesteken]

Filesystem cache. Please, please, search the forum about memory usage and filesystem cache.

 

[apoc]

If you are using zfs it also by default uses up to 50% memory.
Search for ARC limit usage.
And don't forget that PVE itself also needs some memory

 

[Loic92]

ok thanks for the support, following my disk configuration (1TB) I used these commands:
==================================================
vi /etc/modprobe.d/zfs.conf
options zfs zfs_arc_min=4294967296
options zfs zfs_arc_max=5368709120
==================================================
update-initramfs -u
==================================================
echo 4294967296>> /sys/module/zfs/parameters/zfs_arc_min
echo 5368709120>> /sys/module/zfs/parameters/zfs_arc_max
==================================================
2.3.3 ZFS Performance Tips
ZFS works best with a lot of memory. If you intend to use ZFS make sure to have enough RAM available for it.
A good calculation is 4GB plus 1GB RAM for each TB RAW disk space.

3.8.7 Limit ZFS Memory Usage
It is good to use at most 50 percent (which is the default) of the system memory for ZFS ARC to prevent per- formance shortage of the host.

Use your preferred editor to change the configuration in /etc/modprobe.d/zfs and insert:
options zfs zfs_arc_max=8589934592
This example setting limits the usage to 8GB.

Note:
If your root file system is ZFS you must update your initramfs every time this value changes:
# update-initramfs -u
==================================================

 

[apoc]

Try the arcstat command and verify if your values do actually work as expected. I have had once issues that for whatever reason my values where not applied correctly on my first try.

Aside that as mentioned by @leesteken there are other things that need memory.