Does MacOS Support a Snapshot-Style Filesystem?
Solution 1:
Apple's new file system, APFS, supports snapshots. Per their documentation:
APFS is available in 10.12.x (Sierra) as a Developer Preview and as a released product in 10.13.x (High Sierra).
Earlier than Sierra, if you need to make a "point in time" backup, it's best to run Time Machine to ensure a good backup.
Solution 2:
If you can't wait for APFS, you could look into OpenZFS, an implementation of Sun/Oracle's ZFS filesystem. It seems like you can make it work on a macOS boot drive (don't know about Fusion drives), though it's certainly not trivial.