Not getting good network throughput even with LACP bond

[dimante]

I'm seeing full line‑rate performance (around 945 Mbps up and down) from my non‑virtualized devices over a single 1 GbE NIC. My Proxmox host is configured with four NICs bonded in LACP, and the switch side is correctly set up. However, any guest VM tops out at roughly 486 Mbps. I wasn’t expecting reduced throughput with a multi‑NIC LACP bond, so this behavior seems off. For context, I recently migrated from ESXi using the same switch and network configuration, and I did not experience this issue before. It only started after moving to Proxmox. If anyone has suggestions for improving throughput or insights into what might be causing this bottleneck, I’d appreciate the guidance.

 

[jtru]

How exactly do you measure Ethernet throughput performance, which guest OS do you use, and which network devices/adapters did you choose to configure/emulate in your VMs?

 

[dimante]

Thank you for your reply. I use speedtest.net as an internet throughput guide. Let's start with the core windows server 2022 server I have. Here is the vhardware configuration.

Here is throughput from a device on my net (non-virt)

So why is bonded NIC giving 1/2 the throughput. It's very odd to me.

 

[Maximiliano]

The VM is configured to use the e1000 drivers. Please test again with the virtio network drivers. Please note that this requires the VirtIO drivers to be installed, since you already have VirtIO drivers for the scsi controller and the hard disk, this should just work.

See our docs for more details [1]. VirtIO network drivers can produce up to three times the bandwidth compared to e1000.

[1] https://pve.proxmox.com/pve-docs/pve-admin-guide.html#_emulated_devices_and_paravirtualized_devices

 

[dimante]

Ok, you win on that one. The change to virtio has improved it to an acceptable level now:

Though I am still losing a bit on download and upload this is much better. Thank you for the suggestion. I will need to go to the rest of the systems now and fix the network adapters. One question, are there virtio drivers for freebsd?

 

[dimante]

Ok so this server is 100% better but my other Windows server 2022 has the virtio adapter, same host here is the result there:

Here is the config for this server:

Any suggestions here would be greatly appreciated.