A storage unit in the iMac and Mac mini that combines a hard drive (HD) with a solid state drive (SSD). Introduced in 2012, the Fusion Drive automatically moves frequently used data from the HD to the SSD for faster access. Unlike hybrid drives, which have an SSD cache for temporary staging, the Fusion Drive retains the data in the SSD.
No More Fusion in M1 Macs
With the advent of M1-based Macs, storage is all SSD and no more Fusion (see Apple M series
). See SSD
and hybrid drive