Figure 2.14 Configuring Dynamic Memory settings for a virtual machine
Also in the figure are options to set a percentage of memory to use as a buffer and to
use a memory slider to set the memory priority compared to other virtual machines
running on the host. The memory buffer allows you to keep extra memory assigned to
the VM beyond its immediate need. This accomplishes two things. First, it’s not
desirable to let the operating system totally exhaust all memory before adding more
RAM, which may take a few seconds to be added and used. In those few seconds, the
performance of the virtual machine could be severely adversely affected, and it would
have started to page out pages of memory to its pagefile. The pagefile is a file on disk
that can be used by an OS’s virtual memory manager to store pages from RAM
temporarily when physical memory is low. This can deteriorate performance because
disk is much slower to use than RAM. Second, it provides extra memory to be used for