Hyper-V Memory allocation

[jmak]

I couldn't start one of my VMs this morning due to insufficient memory on the host (re-starting my WDS server). The guest was set to require 2GB at startup and there was 11GB in actual use out of 24GB on that host, although significantly more allocated as minimum assigned (16GB). There still should have been plenty to start the additional machine and it has run happily for months at a time in the past. I couldn't quite get to the bottom of it, but by reducing the minimum memory requirements for the VM I was starting all was good. This got me to thinking why should I have such high minimum memory allocation for some of the machines. Is there a reason not to lower the minimum to somewhere close to what is regularly in use, but set it to dynamic memory with a high weighting of prioritisation for important machines?

 

e.g. The DC has a minimum of 4GB allocated, but mostly sits below 2GB utilisation. This seems like a waste of nearly 10% of available capacity. Is there any reason not to set the minimum at 512MB, keep the maximum the same and enable dynamic memory with a high priority?

 

I was thinking DC - low allocation/high priority

File Server - moderate allocation/moderate priority

WDS Server - moderate allocation/low priority (won't be used in anger during main business hours anyway)

 

Thanks