

Every time you look for a file, open a file, move a file, save a file or delete a file, it's the filesystem that is fulfilling that action. The file system also keeps track of how many files you have and how much space they consume.

The file system keeps track of and organizes all of the files on the hard drive, and also determines which users and applications have access to those files. Every user and every application uses the file system. It’s also one of the most transparent, at least when it’s working correctly. The file system is perhaps the most important piece of software on your Mac.
CARBON COPY CLONER 3.4.4 UPGRADE
If the OS upgrade converted my startup disk to APFS, what do I need to do to my backup disk? Do I have to erase it as APFS?.If I first upgrade to High Sierra on an HDD, and then clone to an SSD, will the SSD be converted to APFS?.When I upgrade my Mac to High Sierra (or later), will my startup disk be converted to APFS?.Why is Apple introducing a new filesystem?.You might even be wondering, "What's a filesystem?", so we'll start with that, and gradually move into more technical details. Apple introduced a new filesystem in macOS High Sierra, so naturally you may be wondering how Carbon Copy Cloner deals with this and how this new change might affect your backups.
