High RAM Load PVE Host 8.0.4

[mhert]

Hello.

I have a pve host with several virtual maschines. The host consumes always a high amount of the installed ram. Even if no machine is started.

Some details:



At the moment there are 3 virtual machines running which are configured with 38 GB of ram in total. But as you can see the host comsumes nearly all of the installed memory.



Is this normal or is there something wrong?

When I shut down 2 of the 3 vm's ram usage is still high (the remaining vm is configured with 16GB RAM, but comsumes only 6-7 at the moment):

pve host





runnig vm (server2019):




Storage:






Thanks in advance,

Oliver

 

[leesteken]

Is this normal or is there something wrong?

Could be normal: what did you set your ZFS ARC limit to?

 

[mhert]

 

[LnxBil]

Please post the output of arcstat (as TEXT in CODE tags)

 

[mhert]

arcstat
    time  read  miss  miss%  dmis  dm%  pmis  pm%  mmis  mm%  size     c  avail
12:22:08    14     0      0     0    0     0    0     0    0   17G   17G    18G

 

[leesteken]

View attachment 57084

Since you did not set a limit, ZFS will use up to50% of your host memory.

arcstat
    time  read  miss  miss%  dmis  dm%  pmis  pm%  mmis  mm%  size     c  avail
12:22:08    14     0      0     0    0     0    0     0    0   17G   17G    18G

And it is currently using 17GiB.

 

[mhert]

it's oob...

what's a rational limit?

 

[leesteken]

it's oob...

what's a rational limit?

As much as you can spare? Or as little as still works for you. Note that unused memory is useless and if you don't have a problem, just let the cache do its thing.
ZFS should shrink the ARC when other services need memory but that does not always work quickly enough in practice when starting VMs, in my experience.

 

[mhert]

How can I find out then if the limit is set too low?

 

[leesteken]

How can I find out then if the limit is set too low?

Performance will suffer. As usual: it all depends on your workload and use case. This is not Proxmox specific and there is lots of information about ZFS out there.