Generally speaking, the modern trend in data storage evolution is progressing towards layered data architecture. This is implemented by adding an extra logic layer on a data flow between the storage devices and the file system residing on these devices. This extra layer is processing all read-write requests from the file system, alters the data as needed, i.e. encrypting it, and redirects to one of the physical storage devices (disks or drives) using rules that depend on the layer type and the request itself. In our opinion, the latest macOS High Sierra and Mojave feature 2.5 (two and a half) implementations of this intermediate layer:
RAID arrays (1) + Core Storage (1) + APFS (0.5)
We consider APFS to be half of the implementation, as it’s integrated on the file system level and can only be utilized for itself, while the first two (RAIDs and Core Storage) are full-blown layers that can host other file systems including APFS.
Now getting back to Fusion Drives… it’s actually just a marketing term for a hybrid hardware setup that combines a regular hard disk drive with a solid-state drive into one virtual volume. However, there exist 2 major mechanisms for Fusion Drive implementation, and they are completely different.
#1 HFS+ Fusion Drive with Core Storage
Yes, Disk Drill does support full-featured data recovery from this type of data storage.
In this case, Core Storage is the combining layer. System-level apps like Disk Drill can read any part of the combined volume.
#2 Fusion Drive with native APFS support
This is coming in macOS Mojave and Disk Drill will NOT fully support this configuration right away.
In this case, APFS itself natively combines two disks into one volume. Of course you can access the device data directly, bypassing the logical layer, but this is only a workaround. It is a sad developing story as Apple is not providing almost any technical information, needed for developers like CleverFiles, about APFS.