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Slow connection from on-permise to Azure

We plan to migrate from on-premise to Azure. After deployment of a test virtual machine in Azure tenant we reported a slow connection (download and upload speed) mesured by using iperf:


[ ID] Interval Transfer Bandwidth
[ 4] 0.00-10.00 sec 19.6 MBytes 16.5 Mbits/sec sender
[ 4] 0.00-10.00 sec 19.6 MBytes 16.4 Mbits/sec receiver

Via VPN tunnel the connection is even sload:


[ ID] Interval Transfer Bandwidth
[ 4] 0.00-10.01 sec 18.6 MBytes 15.6 Mbits/sec sender
[ 4] 0.00-10.01 sec 18.5 MBytes 15.5 Mbits/sec receiver

The test virtual machine is not under heavy load, no applications are installed. No other vms are deployed in the virtual network. Someone knows what is causing this issue? We would be very grateful for any tips.

azure-virtual-network
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Can you confirm which VM size you deployed and what type and size of disks you used? The performance of the disks and network interface is software defined based on the size that you deploy.

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ArkadiuszKowalski-7210 answered AlanKinane commented

VM Size: Standard D2s_v4 (2 vcpus, 8 GiB memory)
Sorage type: Standard HDD LRS
Storage Size: 127GB
Storage Max IOPS: 500
Storage Max throughput (MBps): 60
Storage Encryption: SSE with PMK

We tested network performance also by using other Azure tenants with different virtual network topology, different vms size and operating systems, etc in all cases we got about 20Mb / 20Mb (download/upload). We are located in northwest Poland .




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There are a lot of factors in play here.

The disk will only do a max of 60MBps and that VM does a max of 48MBps on uncached storage though it can burst higher but they there are software layers OS, drivers etc that will reduce this further.

You are still accessing it over the Internet so going via ISPs, not a direct connection to your Azure VM.
The VPN has to encrypt/decrypt the traffic.

Is your on-premises firewall scanning the traffic?

I'm not sure which Azure region you have deployed to but your choice might mean you might have a greater distance between your location and where the Azure datacenter is.

IIt all adds up to reduce the actual throughput you receive. What were you expecting to see?

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ArkadiuszKowalski-7210 answered

Probably this issues results from bad interpretation of bandwidth measurement. I was conducting bandwidth tests using iperf. Then I used AzureCT - the Azure Connectivity Toolkit. In general, AzureCT is based on iperf, but it performs more complex tests. In the first case (iperf) I got the result for one tcp session (16 Mbit/sec), in the second case (AzureCT) for 32 simultaneous tcp sessions (489 Mbits/sec), as shown below:

1 Session 16.0 Mbits/sec 0% loss 31.185ms
32 Sessions 489 Mbits/sec 0% loss 31.225ms

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