At maximum a single storage cluster consists 32x HX220c, 32x HX240c, 32x HXAF220c or 32x HXAF240c nodes.
Cisco HX Data Platform supports up to 8 hybrid storage clusters on one vCenter, that equates to 256 hybrid storage nodes.
A hybrid/all-flash storage node cluster can be extended with up to 8/16 Cisco B200 M4/M5, C220 M4/M5 or C240 M4/M5 compute-only nodes. These nodes require the "IO Visor" software installed in order to access the HX Data Platform.
IO Visor: This vSphere Installation Bundle (VIB) provides a network file system (NFS) mount point so that the ESXi hypervisor can access the virtual disk drives that are attached to individual virtual machines. From the hypervisor’s perspective, it is simply attached to a network file system.
Cisco HyperFlex Edge: The storage node cluster configuration consists of 2, 3 or 4 HX220x Edge M5 rack-servers.