[SOLVED] Wrong memory usage monitoring

[BenDDD]

Hi everyone,

I have a problem with the internal memory usage monitoring in the Summary view on my VMs.

Proxmox shows +90% of memory usage but when i SSH into the VM and use htop, it shows -10% of memory usage.

Anyone knows what can cause that ?

Thank you in advance.

 

[Stefan_R]

A bit more info would be needed here... What storage are you using, how much RAM do you have, etc...

If you're using ZFS this could be a result of the ARC caching mechanism using RAM to speed up disk access. Try the output of the following:

free
arcstat

 

[BenDDD]

Hi Stefan_R,

Thank you for your reply.

The VMs hard disks are on an NFS network mount. Each VM have different RAM allocation (2GiB, 4GiB, 6GiB, ...).

 

[Stefan_R]

Still, what's the output of free?

 

[BenDDD]

free on the VM :



Monitoring from Proxmox :

 

[Stefan_R]

So yes, accounting for the Bytes->GiB conversion this is exactly the used memory + caches. That is perfectly normal, RAM caches will be freed as necessary to make room for more "actual" RAM content. In this context, more RAM used is actually better - which is why our GUI reports it this way. 'htop', as you mention, probably doesn't.

 

[BenDDD]

OK i understand. This is troublesome because my monitoring (Centreon + Nagios) shows it as a warning alert as it thinks RAM is completely used.

 

[LnxBil]

OK i understand. This is troublesome because my monitoring (Centreon + Nagios) shows it as a warning alert as it thinks RAM is completely used.

The difference is what the definition of "used" means. For RAM, free is bad, so every OS uses as much as possible for caching. Depending on the system, this cache is sometimes marked as free or not - but if it's needed it'll be freed.

 

[BenDDD]

Thank you for your explanations.