Siemens PLC Sim Advanced Slow OPC tag communication

I'm developing controls for a S7-1500 PLC and Ignition project single PLC communicating with one ignition gateway. I'm using the built in OPC server on the PLC with around 4K tags in the subscription. I'm testing with 2 VMs running on VMware workstation. One machine running ignition and the other PLC sim advanced with communication done over a virtual network on the same physical machine.

I am finding that it can take of order 10-20s for tags to update sometimes. Has anyone else had performance issues with testing with a similar setup? Need to understand if I should be worried about performance after transferring development over to physical hardware.

The laptop I'm running both VMs on is a ryzen 9 with 40gb ram with each VM having 4 cores and 8gb of allocated ram. The laptop runs a little warm but its not maxed out on CPU or ram yet.


I'm not reading in whole data structures from the PLC which I know would help performance somewhat. However I realize now that I set up my datablocks as udt derived rather than defining a udt instance in a global datablock. Ignition doesn't seem to be able to read datablocks as whole structures even if they are udt derived. Anyone know of a way round this?