Cisco HyperFlex has no VMware vMSC certification.
Cisco HyperFlex does not (yet) support stretched clustering for Microsoft Hyper-V.

Cisco HyperFlex Stretched Clustering is only supported for fresh HX 3.0+ installs. Upgrade or expansion of HX 2.x based clusters is not supported.

In HX 3.5 vSphere node expansion workflow is included and supported. HX 3.5 also adds support for HX compute-only nodes as well as HX native replication.

Cisco HyperFlex Stretched Cluster hardware restrictions:
- only M5 supported (no M4 or M5+M4 mix)
- only homogeneus models supported (no HX220+HX240 mix)
- no support for self-encrypting drives (SED)
- external storage is supported, but synchronous replication is the responsibility of the external storage solution.

HX Connect UI (HTML5) is used for managing HyperFlex stretched clusters:
- Cross site HX cluster creation
- Non-disruptive online rolling cluster upgrades
- Site awareness
- Site specific Alarm and Events on a single Dashboard