Since Parallels Desktop version 10 you no longer need to think about the unused disk space in your Windows virtual machine (VM). We have created a feature that takes care of that for you.
The real-time disk optimization feature relies on a TRIM command, which is used in Windows by Optimize Drives option (previously called Disk Defragmenter), and by default runs automatically on a weekly schedule. But you can also optimize drives on your PC manually.
This feature is enabled by default if your Mac's primary hard drive is an SSD drive, and it is available for Windows 7, 8, 8.1 and 10 virtual machines and the OS X virtual machines starting from 10.8 Mountain Lion.
To enable the real-time optimization on the traditional HDD drive you need to shut down your VM -> open your virtual machine's configuration.
For Parallels Desktop 13 and above:
Go to Hardware > Hard Disk 1 > unwrap Advanced Settings > check the Enable TRIM option.
Note: Parallels Desktop 15 provides you the ability to create virtual machines with NVMe virtual hard drives. In this case, the option to enable TRIM will not be presented in the configuration window of the virtual machine because for NVMe disks TRIM should be always working, due to the design of the driver. More information might be found here.
For Parallels Desktop 12:
Go to Hardware > Hard Disk 1 > check the Free Space: Real-time virtual disk optimization option.
NOTE: Real-time virtual disk optimization may affect a virtual machine's performance while doing the compacting (not constantly).
For Parallels Desktop 10 and 11:
Go to Options > Optimization > check the Free Space: Real-time virtual disk optimization option.
How to manage disk optimization settings
- In Windows 8.1 or 10 VM click on Start button > type Optimize Drives > select Defragment and Optimize Drives. (In Windows 7 VM this window is called Disk Defragmenter)
In the opened window you may run optimization manually (1), and configure disk optimization frequency (2):
- Once Windows triggers TRIM for its disks, Parallels Desktop detects it and resizes *.hdd accordingly.
You may also reclaim available disk space manually by following instructions from KB114654.