Azure. When measuring the speed using iperf, the speed does not exceed 30 Mbps

Question

Hello! We have encountered a problem when using Azure virtual servers. When measuring the speed using iperf, the speed does not exceed 30 Mbps. Why is the speed so low? Are there restrictions on Azure servers?

Answer 1

Hi @Yurius Kolgans ,

as per:
https://learn.microsoft.com/en-us/answers/questions/52560/what-is-the-expected-network-bandwidth-for-vm-stan.html
copying the reply by @GitaraniSharma-MSFT :

As per the Azure Compute backend team, the B-series is variable, so they have not published any networking numbers that may not always be accurate. The design of the B series does not provide the user with a consistent level of network performance. In addition, the B series is designed for more CPU intensive workloads as that is what we are really scaling out depending on credits. If network bandwidth is an issue then the B series is likely not the best choice.
You can find more information in the following thread : https://github.com/MicrosoftDocs/azure-docs/issues/8765
If you wish you may leave your feedback here requesting this. All the feedback you share in these forums will be monitored and reviewed by the Microsoft engineering teams responsible for building Azure.

Answer 2

Hello, @Yurius Kolgans !

@Nico Marino is correct here in that the B-series is designed for burstable CPU performance rather than network bandwidth. Still, I've seen higher speeds than what you are seeing on my test B16ms (Windows VM in West US 2) and I've shared a snapshot of some of those speeds in real-world tests below.

To troubleshoot this, it may be worth performing VM bandwidth/throughput testing (NTTTCP) and looking through the documentation on VM network throughput (and perhaps TCP/IP performance tuning for Azure VMs).

I hope this is helpful!

iperf3 across 2 states (65.3 Mbps average)

Google Drive 1GB download (100-130 MBps)

speedtest.net (3,500-4,000 Mbps)

fast.com (1.4 Gbps)