Pascal-9080 avatar image
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Pascal-9080 asked Pascal-9080 commented

Slow azure file share over P2S


I am using Azure File Storage with a P2S VPN to mount file shares over SMB in Windows.
Downloading files through the P2S is extremely slow compared to what I should get, around 1-2mb/s.

I created a file share (directly on the "C" drive in the Windows Explorer) in a Windows VM located in the same Virtual Network in Azure, and mounted this share on my PC using the same P2S VPN and can download at over 50mb/s, which is a lot closer to the limit of the Virtual Network Gateway SKU (VpnGw1)

I tried using the S2S connection and mounting the share and the speeds are a lot faster too.

Mounting the files from inside the VM in Azure ( under the same virtual network ) yields really really fast speeds too.

Here's some info about the Virtual Network and the storage :

Virtual Network
1. Address space:
2. Subnets
2.a. default:
2.b. GatewaySubnet:
3. Both gateway and "default" subnet are connected to the storage service endpoint

Virtual Network Gateway
1. SKU: VpnGw1 ( tried with VpnGw2 too, same results )
2. Point To Site
2.a. Address pool:
2.b. Tunnel type: IKEv2
2.c. Authentication type: Azure Certificate ( I downloaded their "VPN client" to test )

1. Firewall, allow access from: All Networks
2. Private endpoint subnet: default
3. Mounted using the private IP + the keys


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SumanthMarigowda-MSFT avatar image
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SumanthMarigowda-MSFT answered Pascal-9080 commented

@Pascal-9080 Welcome to Microsoft Q&A forum, Thank you for posting your query here!

How much data are you downloading? You can use Azure speed test tool to check the speed:
For testing purpose can you use azcopy tool and check the performance.

This article lists some common problems related to Azure file shares. It provides potential causes and workarounds for when you encounter these problems. Azure file shares performance issues

Additional information: There is no throttling on the Azure side. If the above suggestion doesn't help you! I would recommend you create a technical support ticket to find the root cause of the issue. Since you are getting better speed in the other format The ticket enables you to work closely with the support engineers and get a quick resolution for your issue. If you don't have the support plan we will try and help you get a one-time free technical support. In this case, could you send an email to AzCommunity[at]Microsoft[dot]com referencing this thread as well as your subscription ID. Please mention "ATTN subm" in the subject field.

Thank you for your cooperation on this matter and look forward to your reply.

Hope this helps!

Kindly let us know if the above helps or you need further assistance on this issue.

Please do not forget to "Accept the answer” and “up-vote” wherever the information provided helps you, this can be beneficial to other community members.

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@Sumarigo-MSFT I involuntarily put my reply in an answer. Please see answer bellow.

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Pascal-9080 answered

@Sumarigo-MSFT Thanks for the fast reply,

The "amount / how much" data we are downloading doesn't really matter, the speed is slow whether I try to download 500mb or 5gb. I've performed my tests initially with files between 50mb to 5gb.

I tried the AzCopy and found out there is a benchmark integrated in it.
The "upload" speed is very fast, around 500-600 mbps (through the P2S VPN).
The download is very slow, around 100mbps, which is faster than I was getting "manually" with the Windows Explorer but it is to be expected with the benchmark.
The benchmark seems to be accusing the network speed, which shouldn't be a problem. My internet connection is fast enough, and I am able to download at much much faster speed between my PC and a virtual machine in azure, through the P2S VPN.

I tried running the benchmark through the S2S VPN and it is going around 500mbps too. The problem seems to be limited to the combination of P2S and Azure File. Any other combination (S2S + Azure File, P2S + VM, etc...) yields fast throughput.

Finally, I have also tried uploading / downloading with azcopy in a blob in the same storage account, and the speeds are very high in both the download and the upload, leading me to believe that the Azure File is the problem. Which fits with the other tests, Ex. I can download fast when downloading from a VM in the same virtual network in the same subnet. What I do not understand is why it is fast to download from the Azure File storage account when going through the S2S VPN.

We do not have any support plan indeed, which is why I came to here first!


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