High Memory During Backup

[jjtech]

Hello, I'm fairly new to proxmox and running into some trouble with backups. I configured a VM backup job writing to an NFS share with mostly default options (Snapshot, ZSTD compression). Within a minute or two of starting, the system and all VM's became unresponsive. After rebooting I tried again while watching system resources. My proxmox host has 16GB memory, about half of which is generally free. During the next backup attempt, I watched the memory fill up until everything became unresponsive again.

The answer might be as simple as, "you just need more memory or it won't work", but I'm not sure if I'm missing any critical configuration. Any help appreciated.

 

[Kingneutron]

Can you backup to local storage and then move things to NFS?

 

[leesteken]

While a backup runs, new write actions need to be buffered to assure consistency. Maybe that's what takes up all your memory if the backup takes a while? Do you have the same problem when the VM is not running during a backup?

 

[jjtech]

Can you backup to local storage and then move things to NFS?

A bit more hassle, but I can try that and see if it makes a difference in case there is some bottleneck with the NFS I guess. Thanks for the idea.

While a backup runs, new write actions need to be buffered to assure consistency. Maybe that's what takes up all your memory if the backup takes a while? Do you have the same problem when the VM is not running during a backup?

That makes sense I suppose. I tried pausing the VM's first. It went better, but still failed. With them running usually it failed about halfway through the first VM. This time it finished the first and got to 97% on the second, hovering around 300MB free memory the whole time, but then became unresponsive again.

 

[Kingneutron]

How much swap do you have allocated?

 

[jjtech]

How much swap do you have allocated?

I don't think I've ever explicitly changed anything there. Looks like 8 gigs.

free -h
               total        used        free      shared  buff/cache   available
Mem:            15Gi       6.4Gi       8.7Gi        32Mi       562Mi       8.9Gi
Swap:          8.0Gi          0B       8.0Gi