How Disk Images and VMs Are More Efficient
What happens with an Apple silicon VM is a bit more complicated, and harder to observe. This time the virtualisation app should create the disk image inside the VM bundle as a sparse file to begin with, then copy into that what’s needed for the VM, so skipping the first mount stage and Trimming during the second mount.
The result is the same, though, with a 350 GB VM taking just 22 GB on disk. Inspect that disk image using my free utility Precize, and you’ll see that economy confirmed, and the Sparse File flag set.
He has a summary of the requirements for “plain read-write disk images and those inside VMs to be sparse files.”
Previously:
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What I really want to know, though, is what happens when the guest does a TRIM on the virtual disk. Will virtualization.framework sparsify those regions of the image that are being trimmed? I'll probably figure it out soon enough as my VMs TRIM enough space, but it would be nice to have some testing on this.
