User`s guide

Troubleshooting and Limitations 234
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 (p. 66) 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 (p. 171) 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
(p. 176).
Reason 6 - Parallels Desktop creates detailed log messages
If you select Use detailed log messages in the Advanced pane (p. 53) 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.