In Ventura, VM disk performance was poor, with write speeds of 0.7 GB/s. How fast is it now in macOS 26.4, and how does using FileVault affect it? Plus a note on problems with BSIs in VMs.
disk image
When trouble strikes a disk image, macOS normally refuses to accept and mount it. This details how to use hdiutil to attach the image as a device so it can be repaired by fsck_apfs.
The new ASIF disk image type is now 18 months old. How well does it perform? Is it as good as claimed? It all depends on whether you want to use encryption.
They come in a multitude of formats and variants, and are used throughout macOS and apps. How do you use them, and what should be wary of?
This new disk image format is claimed to be “efficient and general-purpose”. But is it? Is it as fast as sparse bundles or read-write (UDRW) disk images are?
ASIF disk images are new in Tahoe, and promise to be space efficient, as they’re sparse files, and almost as fast as the disk they’re stored on. Ideal for VMs and general use.
Read-write and VM disk images are created and maintained differently, but they can both be APFS sparse files. Explanation of their creation and maintenance.
How read-write disk images and those used in Apple silicon virtual machines use sparse file format to save space on disk.
From their use to replicate floppy disks in manufacture, to their key roles in macOS, for distribution of software, and on network servers to contain backups. Unglamorous but essential.
Why does compressing a 15 GB file within a sparse bundle run more slowly than would be expected from its write performance?
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