These issues may occur due to a lack of free disk space on your Mac.
A Fusion virtual machine needs disk space on the Mac for both the virtual machine's memory (assigned RAM) and for the virtual machine disk files (assigned virtual disk size).
To ensure that your Mac has enough disk space for your virtual machine:
- Determine available disk space.
- Determine the amount of virtual memory assigned to the virtual machine.
- Calculate the difference between the allocated size of virtual disks and the current size of the main virtual disk. This difference is the amount of disk space the virtual machine can grow to fill, not counting any later snapshots.
Note: If you chose to pre-allocate your virtual disk, this step is unnecessary.
- Confirm that the free space is sufficient.
Note: This step basically confirms that the free space (Step 1) is greater than the sum of the assigned virtual memory (Step 2) and the amount of disk space the virtual machine can grow to fill (Step 3).
Determining available disk space
For example purposes, let's say you have 5 GB of available space.
Determining the amount of virtual memory assigned to the virtual machine
To determine the amount of virtual memory assigned to the virtual machine:
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Open Fusion.
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Select the virtual machine.
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Go to Virtual Machine > Settings....
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Click Processors & RAM. The assigned virtual memory (RAM) size is displayed in MB.
For example purposes, assume you have 1GB of RAM assigned to your virtual machine.
Calculating the difference between the allocated size of the virtual disks and the current size of the main virtual disk
If you did not pre-allocate your disks, the virtual machine starts with small virtual disks. The virtual disks can grow in size until they equal the allocated size. To calculate the difference between the allocated size of the virtual disks and the current size of the main virtual disk, take the allocated size of the virtual disk and subtract the current size of the virtual disks.
- To determine the allocated size of the virtual disk:
- Open Fusion.
- Select your virtual machine.
- Go to Virtual Machine > Settings....
- Click Hard Disks. The allocated disk size is displayed in GB.
For example purposes, let's say you have allocated 40 GB to your virtual machine's disk.
- To determine the current size of the virtual disks:
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Ctrl-click each .vmdk file and select Get Info. The size of the virtual disk is displayed in the top-right corner of the Get Info window.
- If you have multiple .vmdk files, add the size of each together to find the total size.
For example purposes, let's say you have 20 virtual disk files, ranging in size from 684 KB to 2.1 GB, and the total size is 30 GB.
Confirming that the free space is sufficient
The difference between the size of the virtual disk allocated to the virtual machine and the current size of the virtual disks, plus the amount of assigned virtual memory, must be less than the currently available free disk space. Otherwise, Fusion does not let the virtual machine start because the virtual machine might grow to be larger than the physical disk.
If you have 5 GB of free space, your virtual machine will not start unless it requires less than 5 GB more space
Using the examples from this article, if you have a virtual machine with 1 GB of assigned RAM, an allocated size of 40 GB, and non-pre-allocated disks totaling 30 GB, then your virtual machine needs 11 GB more space: 1 GB for the assigned RAM and 10 GB for the difference between the allocated size and the current size of the virtual disks (40 GB - 30 GB = 10 GB).