Slow VM Backup After Unexpected Reboot (Exchange Server)

[vescovialex]

Hi everyone,


I'm reaching out for some assistance with a backup slowdown issue I'm experiencing on Proxmox VE. Two days ago, my on-premises Exchange server encountered a freeze and required a hard reboot, which took longer than usual to complete.


Since the reboot, I've noticed a significant decrease in VM backup speed. This issue seems to be specific to the Exchange server VM. While backups for other VMs are running normally, the Exchange server backup takes around 8 hours to complete, with the slowdown occurring after the initial 25% mark.


Here's a breakdown of the situation:

• Affected VM: Exchange Server
• Backup Issue: Slow transfer rate after initial 25% progress
• Backup Destinations:
  • NAS via NFS (HDD)
  • Proxmox Backup Server (PBS) (HDD)
• Storage: VM resides on SSD disks
• Troubleshooting Steps Taken: Defragmented the VM storage (uncertain of effectiveness)

I've attached a screenshot of the previous day's backup progress on the NAS for reference.


Any insights or suggestions on how to diagnose and resolve this backup slowdown problem would be greatly appreciated. Thanks in advance for your help!

 

[vescovialex]

A little update:

The Problem:

• My SSD usage jumps to 100% in Task Manager whenever a backup starts (using Windows).
• This 100% usage persists throughout the entire backup process, causing significant slowness.
• I've run multiple scrub tests on all my disks, but the problem remains.

What I've Tried:

• I created a VM (with qemu-agent installed) for testing purposes, and the OS install is ridiculously slow, further indicating a performance bottleneck.
• To isolate the issue, I tried backups on another proxmox installation, and the HDD usage behaves normally during backups there.
• I've even tested backing up to an external HDD and using my PBS, but the situation remains the same across all storage types.

Looking for Help:

I'm completely stumped! Why is only my system experiencing this extreme SSD usage during backups?

Any insights or suggestions would be greatly appreciated. Here's some additional info that might be helpful:

• Have you encountered similar issues with high HDD usage during backups?
• What troubleshooting steps could I try next?
• Could qemu-agent be contributing to the problem?

Thanks