What happens if a CloudStack Management Server goes down?

No.

The Management Server is primarily the control plane. A running VM is actually executing on the hypervisor host.

So you should distinguish between:


Management Plane
→ CloudStack Management Server

Compute Plane
→ KVM / other hypervisor hosts

A Management Server outage doesn’t automatically mean that every running VM stops.

However, management operations such as provisioning, configuration changes, and other CloudStack API/UI operations can be affected.

This is one reason production CloudStack environments may use multiple Management Servers.