VMWare Performance - vmem file cause harddisk IO busy

I am doing my project work on a vmware virtual machine. I normally will let the vm running over night. The issue is that the VM will hang for at least 15 min everyday morning when I wake it up.

After some investigation, I found there are huge read and write activities on the the *.vmem file in the virtual machine folder. It turns out the vmem file is the backup of your VM's memory. If your VM's memory is big, e.g. 8Gb, there will be a lot of writing to backup the memory to harddisk. 

You can change it by ask vmware to save the memory backup in your host machine's RAM. The catch is that there is no GUI to help you therefore you have to manually modify the vmx file. However it is a easy change. All you need to have is the following line in you vmx file.

mainmem.useNamedFile = "FALSE"

Reference: http://faq.sanbarrow.com/index.php?action=artikel&cat=78&id=76&artlang=en