Understanding the way Mac OS X allocates memory can help to identify potential problems. It also gives you a more comprehensive understanding of how Fusion and its virtual machines use the Mac's memory.
This article provides information about system memory (RAM). For information about disk space, see Investigating disk space in Mac OS X (1021932).
When a virtual machine is powered down, it is assumed that you will not be starting it any time soon. Therefore, the majority of the memory is returned to inactive memory. This ensures that other programs can use the available memory.
When a virtual machine is suspended, it is assumed that you may resume the virtual machine a few moments later. Therefore, the contents are stored in the active memory to ensure a much quicker loading when you resume the virtual machine. While Fusion is running, the suspended virtual machine's memory state will remain in active memory. When Fusion is shut down, then the virtual machine's memory state (which is stored on the hard drive for later use) is moved into inactive memory.
For information on how Mac OS X handles memory, see the Apple Knowledge Base article HT1342.
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