Product : Cisco, HyperFlex [HCI]/4.0, x86
Feature : Hypervisor OS Layer, General, Storage Support
Content Owner:  Herman Rutten
Summary
Dual SD cards
SSD (optional for HX240c and HXAF240c systems)
Details
Each HX node comes with two internal 64 GB Cisco Flexible Flash drives (SD cards). These SD cards are mirrored to each other and can be used for booting.

The HX240c and HXAF240c models also offer the choice to boot from a local 240GB M.2 SSD drive that is connected to the motherboard.