High I/O Delay in Proxmox 8.4.1 With Kernel 6.8.12-10-pve: How to Revert to a Stable Version

Following the upgrade to Proxmox VE 8.4.1 with kernel 6.8.12-10-pve, multiple users have reported abnormal increases in I/O delay within their systems. This issue appears to be related to the newly introduced kernel version and can be resolved by reverting to a previous stable kernel, such as 6.8.12-9-pve or 6.5.13-6-pve.

🔍 Symptoms

• High I/O delay shown in the Proxmox web interface (pve-manager).
• General VM or LXC container sluggishness.
• Disk latency issues not caused by hardware problems.

✅ Temporary Fix: Set a Previous Kernel via GRUB

You can solve the issue without removing the new kernel by configuring your system to boot from a previous kernel version.

1. List GRUB Entries

Run the following command in your terminal:

cat /boot/grub/grub.cfg | grep menuentry

This will display all available GRUB boot options, such as:

menuentry 'Proxmox VE GNU/Linux, with Linux 6.5.13-6-pve' ...
menuentry 'Proxmox VE GNU/Linux, with Linux 6.8.12-9-pve' ...
menuentry 'Proxmox VE GNU/Linux, with Linux 6.8.12-10-pve' ...

2. Edit GRUB Configuration

Open the GRUB configuration file:

nano /etc/default/grub

Locate this line:

GRUB_DEFAULT=0

Replace it with the appropriate entry index or name. For example, if the desired kernel is the fourth in the list:

GRUB_DEFAULT=3

Or use the full entry name in quotes for better reliability:

GRUB_DEFAULT="Proxmox VE GNU/Linux, with Linux 6.8.12-9-pve"

⚠️ Note: The index number may vary between systems—check your list carefully.

3. Update GRUB and Reboot

Save your changes, then update the GRUB bootloader:

update-grub

Finally, reboot your system:

reboot

Once booted, verify the system is using the intended kernel and that I/O delay values have returned to normal.

🛠️ Extra Tip

To prevent accidental boot into the problematic kernel in the future, you may optionally uninstall it or continue using the manually defined kernel selection as default.

🧩 Conclusion

Performance issues after kernel updates are not uncommon in complex virtualization environments like Proxmox. Reverting to a previously stable kernel is often the most efficient way to troubleshoot unexpected delays.

If you’ve experienced similar behavior with recent Proxmox kernel versions, consider sharing your findings to help others in the community.

via: Linkedin