My Journey from Infrastructure Admin to Cloud Architect: Navigating vSAN Clusters without vCenter

As an infrastructure admin, I have always been familiar with the power of vSAN in creating robust and efficient virtualized environments. However, when faced with a scenario where vCenter is down and the cluster needs to be reconfigured, I found myself on a journey to explore alternative methods for forming and managing vSAN clusters without the need for vCenter. In this blog post, I will share my experience and the steps I took to successfully navigate this challenge.

The Challenge

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In a nested vSAN environment, we often encounter situations where vCenter is down or not functioning properly, resulting in inaccessible data and an inoperable cluster. This can be a major setback for organizations relying on virtualized infrastructure to support their business operations. To overcome this challenge, I needed to find a way to form and manage vSAN clusters without vCenter.

The Solution

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To begin, I assessed the situation using the vSAN Health in ESXi web interface. This tool provided valuable insights into the state of the cluster, revealing that all hosts were isolated and unable to communicate with each other. To address this issue, I employed a series of commands and techniques to manually inform the hosts about their vSAN neighbors and recreate the cluster without vCenter.

Step 1: Check Cluster Status

The first step was to check the status of the cluster using the esxcli vsan cluster get command. This confirmed that all hosts were isolated and unable to form the cluster.

Step 2: Check Network Connectivity

Next, I used the vmkping -I vmkX x.x.x.x command to check if the network connectivity was the issue. Fortunately, the pings were successful, indicating that the network was functioning properly.

Step 3: Manually Inform Hosts about Neighborhood

Since vCenter was not available, I needed to manually inform the hosts about their vSAN neighbors. This is typically done through unicast communication, where each host communicates with its neighbors directly. To do this, I used the esxcli vsan cluster unicastagent list command to check the list of neighbors for each host.

Step 4: Add Hosts to Unicast Agent List

To form the cluster without vCenter, I needed to manually add hosts to the unicast agent list. This ensures that each host has a complete list of its neighbors, allowing them to communicate and form the cluster. To do this, I used the esxcli vsan cluster unicastagent add command, specifying the host UUID, the IP address of the host, and the port number (12321 in my case).

Step 5: Check Sub-Cluster Member Count

After completing these steps, I checked the sub-cluster member count to ensure that the cluster was formed successfully. To my relief, the count had increased from 1 to 4, indicating that the hosts were now able to communicate and form the cluster without vCenter.

Conclusion

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In this blog post, I have shared my journey from infrastructure admin to cloud architect, navigating vSAN clusters without vCenter. By using a combination of commands and techniques, I was able to successfully recreate the cluster and make the data accessible again. This experience has taught me the importance of being adaptable and finding creative solutions to overcome challenges in virtualized infrastructure management.