How much does actual writing occur to the ssd when VirtualBuddy creates a disk file on the mac?

[muratyildiz0b]

Hi,
I'm curious about how much writing can occur on the ssd when VirtualBuddy creates a disk file. I created a sonoma VM on my mac and the software created about ~130 GB file. I think it is mostly empty and just allocated some space for the VM but I'm not a programmer so I decided to ask for the details. Does deleting and creating VM files take a toll on the ssd?
Thanks.

[insidegui]

The specifics of how creating/deleting VM files may affect your SSD will depend on the filesystem being used. Your Mac's internal SSD is most likely using APFS, in which case it is not actually writing/erasing 130 GB for the VM, it's just creating a file that reports having that size.

If you right-click and select "Show Package Contents" for the VM, then "Get Info" on the Disk.img file, you can find out what's the actual storage capacity the file is currently using.

In the screenshot below, even though the disk file is reported as 137.44 GB, it is only actually using 17.09 GB (the "on disk" information under "Size:").

The Virtualization framework that's used by VirtualBuddy synchronizes the VM's storage periodically, so it's not constantly writing to the disk image. Even if you have a disk image that's actually taking 130 GB of storage, deleting it is not a big deal because the filesystem is not going to write over the file with zeroes, it just marks the file as deleted and frees that space for more data to be written in the future.

If you'd like to learn more about this, you can search for APFS and find links about how it handles disk space (it's quite complicated).

[muratyildiz0b]

Thanks for this very informative answer.

Best regards