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I have Windows Server 2012 R2 running on a regular workstation. I had set up HyperV and created a server2012 VM. My transfer speeds were fast from my PC to the host/VM, but it seems after running windows updates on the host and VM, transfer speeds to host/VM do not exceed 1MBs.

I disabled virtual machine queues, and also enabled jumbo packets but this did not do anything. I also created a NIC team and speeds are the same.

Transferring files from the Hyper-V Host or Guest to my PC is very fast, around 150-200 MBs but slow transferring from My PC to the Hyper-V Host or Guest, around 500-700KBs.

I have other servers and clients on the same switch that are not experiencing this problem, what could be going on?

Dave M
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arealhobo
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1 Answers1

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I believe this is the TCP Offloading feature which causes problems on virtual machines.

It is a feature of the network adapter and driver. Go in to control panel > network settings > change adapter settings. Right click the network adapter and click configure and then choose the advanced tab.

Disable all options that say 'offload' or 'offloading'. You may have to do this on the guest and host. Try each or both and test. At this point I can't remember which I changed it on.

Appleoddity
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  • I just disabled everything that said offload or offloading on each adapter, nic team, virtual switch and the adapter in the guest vm. Just tops out at 1MB transffering to host/guest. VMQ are disabled and Jumbo packets enabled. Going to double check everything. – arealhobo Aug 28 '17 at 15:44
  • Speed and duplex are also set to 1GBS full duplex. – arealhobo Aug 28 '17 at 15:47
  • You might want to disable jumbo packets, at least for testing. Unless every device between and including each endpoint supports jumbo packets you might create problems like this. When doing speed tests make sure you keep your packet size below your MTU - Overhead if you have a choice. – Appleoddity Aug 28 '17 at 15:50
  • Still no luck, disabled jumbo packets on the adapters, nic team, virtual switch and inside the VM. Also the guest vm uses a different adapter than the host, and the host has the same issue. Going to try this on the host adapter, then also remove the nic team and use a single adapter for the vm. – arealhobo Aug 28 '17 at 16:06
  • Holy cow, it was the TCP offloading! But I did not turn it off on my PC. I tried a file transfer from another server to the server with the issues and there were no problems sending and receiving, so it made me realize its my machine sending files slow. Disabled TCP offloading features and now I am getting 100MB+ send and receive. Still find it odd that once I ran windows updates on the target host/vm, everything became slow. – arealhobo Aug 28 '17 at 16:14
  • Yeah that is strange. Shouldn't be an issue on the PC. – Appleoddity Aug 28 '17 at 16:16
  • Thank you for your post!! disabling all offloading items in the NIC helped, this is still an issue on the latest version of HyperV my set is... Windows 2022 host, various guests ranging from windows 2019,2022, win 11 22h2, some linux, etc HyperV guests could not copy large files at all to other guests but iperf was reporting 25-30Gbit/s to both other guests and hosts guests reside on a fast M.2 that is capable of 7.5GB/s, main disk storage is capable of 1GB/s on spinning drives (4x16TB in raid0). another guest residing on an M.2 can do 5GB/s, nothing should be going less than ~800MB/s even wit – user1007318 Mar 01 '23 at 00:48