Q. I've heard that if I'm using Dynamic Memory and the Hyper-V host could have memory constraints, increasing the size of the guest OS pagefiles is a good idea. Why?

A. Hyper-V Dynamic Memory will only allocate memory to a virtual machine (VM) if there's physical RAM available, or RAM that can be reclaimed from another VM that has a lesser need (priority). Sometimes this reclaiming could take a small amount of time, or there could simply be none available, so having a larger pagefile in the guest OS allows the guest OS to make intelligent choices on the memory pages that are least important and can be swapped out to disk, freeing up RAM for other processes. If the guest has a very small pagefile, it has limitations on the amount of RAM it can page to disk, so increasing the pagefile simply gives the guest OS greater flexibility in its paging choices. Obviously, in an ideal world you don't want much paging, and you should be sizing your environments as accurately as possible.