The amount of RAM used for the desktop affects both the amount of storage space required and the likelihood that it will need to swap memory into the Windows page file.

Windows initially sizes the C:pagefile.sys system file based on the amount of RAM the virtual machine is granted. From that point forward, the file expands as needed in response to Windows OS virtual memory requirements. The page file will also increase in size when the desktop RAM is increased.

The amount of RAM assigned to the virtual machine affects whether it is likely to need to utilize the Windows page file. Using the page file generates additional storage I/O, which we prefer to avoid in a Horizon environment where the storage is shared among multiple desktops. Using the techniques described in Chapter 1, VMware Horizon Infrastructure Overview, the desktop should be assigned sufficient RAM so that, under normal circumstances, it will not need to use the page file.

The Microsoft TechNet article Pushing the Limits of Windows: Virtual Memory (https://blogs.technet.microsoft.com/markrussinovich/2008/11/17/pushing-the-limits-of-windows-virtual-memory/) contains additional guidance about how to properly size Windows system RAM.