If Your Virtual Machine Is Slow

The most common reasons why a virtual machine becomes slow are as follows:

Reason 1 - Not enough memory or CPU time on your Mac

If you run a number of memory-consuming applications on your Mac and a virtual machine simultaneously, the virtual machine performance may become slow because your Mac does not have enough memory or CPU time. In this case, use Activity Monitor (Mac OS X utility) to view what applications consume your Mac's memory. If you do not really need these applications (for example, you forgot to close them or you are going to use them later), quit them.

Reason 2 - Not enough memory set to the virtual machine

The amount of memory set to a virtual machine by default is usually enough for the guest operating system and applications that do not consume much memory (for example, Microsoft Office). However, if you run memory-consuming applications, you need to increase the amount of memory set to the virtual machine. You can do this on the General tab of the virtual machine configuration.

Reason 3 - Antivirus software may slow down your virtual machine

Your virtual machine may become slower after you install antivirus software in it. To be protected, you have to sacrifice performance.

Note: Do not install more than one antivirus application in a virtual machine.

Reason 4 - The virtual machine is running from an external storage

If you start a virtual machine stored on an external storage connected to your Mac (for example, an external USB disk drive), its performance will be lower than of the same virtual machine stored on your Mac.

Reason 5 - The virtual machine is not tuned for speed

To speed up a Windows virtual machine, select Tune Windows for speed in the Optimization pane .

Reason 6 - Parallels Desktop creates detailed log messages

If you select Use detailed log messages in the Advanced pane of Parallels Desktop Preferences, Parallels Desktop will start creating a more detailed log file. It can be helpful for the Parallels support team, but uses more hard disk space and may slightly lower the system performance.