VMware Virtual Machine Thrashing Hard Disk

April 22, 2010

In a previous post I discussed how I had been having issues with an incompatibility between the VMware “.vmem” file and antivirus software.

It turns out that a similar disk thrashing issue has been occurring while the VM is running… but this time is occurs randomly. For some reason, VMware decides to perform an almost endless number of reads from the “.vmem” file for at least 15 minutes and thus crippling system performance.

I solved this problem by disabling the usage of the “.vmem” file.

Unfortunately VMware Player does not have a UI setting for this, so I opened up my virtual machine’s VMware “.vmx” settings file and appended the following:

mainMem.useNamedFile = "FALSE"

With this setting, VMware no longer creates and uses the “.vmem” file, and instead relies on the Window’s host machine to use its own paging file, only if and when it is actually necessary.

The only time the “.vmem” file is temporarily created is if you save the virtual machine state (similar to hibernation) instead of shutting down the machine.

The virtual machine now has excellent performance characteristics!