VMware Workstation 16 Pro - networking issue in combination with Windows XP/ DOS application

[ltw001]

Hello, 
I got a client with a really special setup and may need your help please.
I converted some physical Windows XP machines running some really old DOS-like software to VMs running on Windows 10 hosts. 
The DOS-like software is opened via LAN (bridged mode) and connects to a network share on another XP VM on another Windows 10 host. That works as expected, but:
There is a function inside the DOS-like software which reads a client list. 
This took 5 minutes max. before the XP machines where virtualized.
Now it takes over 30 minutes. (for about 216MB in total - consisting of 10.000 client entries)

I tested the hosts und VMs network connections (Gigabit - virtual and physically) by copying files -> everything fine and fast.
I also changed the virtual network cards as discribed here: https://communities.vmware.com/t5/VMware-Workstation-Pro/slow-guest-network-performance/td-p/1802610

I'm assuming that the issue is caused by a lot of small sized data but a huge amount of it being transferred.
-> Is there a way to tune the network connections for "small data packages"?

In addition (perhaps there is a connection to the issue above): From time to time the DOS-like software closes itself and seems like it could not communicate with the network share for a moment.
After opening it again, it works again immediately...until the error occurs again.

I would really need help with this!

Thanks a lot in advance!

best regards

[ltw001]

Hello again,

seems like it is a quite challenging issue. 

Is there a way to get professional support directly from VMware? (it is a paid pro version of the product)

Thanks again!

[scott28tt]

I believe you can pay for per-incident support: https://www.vmware.com/support/contacts.html

[bluefirestorm]

This is really bad technical debt still being paid after over 20 years (XP came out in 2001). I doubt if it is really a DOS program. It is likely some application written purely just for command line. A DOS program would have been 16-bit and DOS does not have built-in networking. If it is really a DOS program, the technical debt is even longer.

Anyway, as for performance.

Make sure that the Windows 10 hosts does not have Hyper-V enabled. With Hyper-V enabled, VMware Workstation hypervisor is slower as it goes through a Windows Hypervisor API compared to the native Intel VT-x hypervisor. You can confirm which hypervisor is being used in the vmware.log of the VMs.

<timestamp> | vmx| I005: Monitor Mode: ULM

If it shows ULM that means Hyper-V is enabled. If it shows CPL0 instead of ULM, it is using the faster hypervisor.

What are the CPU models in the two separate Windows 10 hosts? You probably want at least Intel Haswell CPU for the host machines; possibly Kaby Lake or newer if you can't disable Hyper-V for IT policy reasons.

No idea about why the program closes itself, it might be a bug that has been there all these years and now manifests itself in a VM. Closing itself is likely a form of program crashing. That is part of the long term technical debt.