The Vcenter is a management tool for the three nodes, effectively combining the individual nodes (see The paper) into a single converged cluster.

Before working with the Vcenter, please, please, please refer to the documentation. A good starting point is the VMware Docs. Be aware that these resources are very detailed and in-depth.

The Vcenter is hosted at vcenter.sleep.ru.is.

The Vcenter is delicate, and the level of expertise required to manage the VMs and maintain the system cannot be overstated. Any misconfigurations can lead to severe issues, often necessitating intervention from Netters or Cisco for debugging, updates, and general maintenance.

“I cannot emphasize how badly it can go for us if this thing is misconfigured. We've already spent hours and hours trying to figure out licensing, which finally had to be fixed by a Netters technician who himself had to spend hours doing it.” - Benedikt

Only people whose work is administrating the cluster.

Scheduling maintenance should be done considering 2 main issues, usage patterns (make sure that a minimal amount of work is disturbed), and ongoing projects (if a big data collection project is ongoing, maintenance should probably be delayed for the system itself.