Where does Fault Tolerance store the primary and secondary virtual machine files?

Restricting FT to local storage only would prevent secondary VMs from being placed on hosts where shared datastores are used, contradicting the vSphere 6.x design that explicitly supports shared storage as well.

While shared storage is common in vSphere environments, vSphere 6.x FT does not mandate it - local storage is a fully supported option for FT disk file placement.

vSphere 6.x introduced a redesigned FT architecture using Fast Checkpointing, which gives each FT VM its own independent set of virtual disk files rather than sharing a single VMDK on shared storage as in older versions. Because files are managed independently per VM, they can reside on shared datastores or on local storage accessible only to their respective host. This dual storage support removes the strict shared-storage requirement of legacy FT deployments.

SSD refers to a physical storage medium type, not a storage access model - FT placement requirements are defined in terms of shared versus local accessibility, not by underlying media technology.