Proxmox VE high RAM usage after backup to PBS

[lokas]

I’m running PVE 8.3.3 on an intel i7-12650h with 32GB of RAM. It currently runs one VM and a handful of LXCs.

Typical RAM usage for the entire node is around 10GB and seems to be pretty stable.

I have a Proxmox Backup Server running on another machine with a daily backup job. As soon as the job runs the RAM usage on the PVE node jumps to around 25GB and remains there even after the backup has completed.

A restart of the node brings the usage back down, but only until the backup job has run again.

Any ideas on what could be causing this behaviour?

 

[cheiss]

As soon as the job runs the RAM usage on the PVE node jumps to around 25GB and remains there even after the backup has completed.

Probably file system/page cache. There are lots of threads about this topic.
See also e.g. https://www.linuxatemyram.com/

What filesystem do you use? Especially with ZFS this is to be expected, depending on the configured ARC.

 

[severferdi]

Hello,
I'm experiencing the same issue. It worked fine in 8.4, but after updating PBS to version 4.X, I experienced the same issue. When PBS is restarted, RAM usage is quite low, but when nightly backups start, RAM usage peaks and doesn't decrease until I restart the server after the job is completed.

P.S : I'm using ZFS but as I mentioned above, there were no problems with version 8.4. The problem started occurring after upgrading to 4.x.

 

[leesteken]

The new ZFS version (that comes with the new Proxmox) has a default maximum of 90% of memory, while the previous versions had a default maximum of 50%. If you never set a memory limit before, this is a big change. Maybe manually configure a limit (of 10% or so?): https://pve.proxmox.com/pve-docs/pve-admin-guide.html#sysadmin_zfs_limit_memory_usage

 

[severferdi]

The new ZFS version (that comes with the new Proxmox) has a default maximum of 90% of memory, while the previous versions had a default maximum of 50%. If you never set a memory limit before, this is a big change. Maybe manually configure a limit (of 10% or so?): https://pve.proxmox.com/pve-docs/pve-admin-guide.html#sysadmin_zfs_limit_memory_usage

Thank you leesteken. I made the necessary changes. I'll let you know if it worked when the nightly backups are complete.

 

[severferdi]

The problem has been solved as leesteken suggested. Thank you very much.