What can cause low copy speeds for very large and possibly sparse files, such as VMs? Causes explained, and tools you can use to discover why.
sparse file
Sparse files are now common among databases, disk images, and virtual machines. How they work in APFS, how they’re created, and how they can explode.
Overview of clone files, dataless files, sparse files, symbolic links, and firmlinks, and how used and free space is accounted for in APFS.
Introduced in iOS 10.3 on 27 March 2017, then in macOS 10.13 six months later. It ups and downs, and where it still has further to go.
How local files retain their extended attributes and versions when moved to iCloud Drive, but they’re not available to other Macs. Sparse files and storage economy as well.
Why did that progress dialog suddenly vanish long before it had even reached 50% of the copying progress?
Knowing a little about sparse and clone files in APFS is dangerous, as it can lead you to draw the wrong conclusions.
What’s in APFS, and what are its tools? How to interpret the version number, and what do we know has changed with different versions? How compatible are they?
How to protect collections of files using different encryption passwords, and making most efficient use of storage space.
So how can a VM of 119.6 GB fit in a 100 GB container? How sparse files can make VMs and disk images smaller on disk.
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