vSAN Is Lost Without vCenter, or Is It?

There were some confusion from partners and customers that vSAN will fail if vCenter is down. So is it really?

If you are not interested in reading the rest of the post, heres the quick answer.

vSAN & vCenter are totally independent of each other and vSAN will continue to run even without vCenter.

Assuming you had a vSAN cluster all setup and configured today, running production workload. Someone then accidentally powered off the vCenter server, technically, nothing is going to happen to the vSAN environment. IOs will continue to flow, data will continue to be written, and cross site replications continue to protect. 

There are no dependencies at all with regards to the up-time and availability of vSAN with the loss of vCenter. To extend this further, we have recently also built-in vSAN Health Check directly into vSphere Host Client UI. If vCenter becomes unavailable, users can directly connect to each individual vSAN Host to view the Health Status of all the vSAN components. With vSphere 6.7, it is now presented in HTML5! 

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Figure 1 : vSphere Host Client - vSAN Health Check

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Figure 2 : Details right up to drive congestions

Given that vCenter is the defacto management tool for vSphere environments, it provides many functions and capabilities that is not necessarily available through individual vSphere Host Clients. For example, vMotion. vCenter is key for cluster management because it provides a birds eye view of the interactions between members / participants of the cluster. Cluster awareness is important in the world of vSAN because storage capabilities and functions are a collective of members participating in the vSAN cluster.

Having said that, while the loss of vCenter does not impact the availability and functionality of vSAN, we do lose some advanced management capability. For example, we can't create new Storage Policies or change VM policies, or perhaps create a new stretched cluster. While not ideal, it is probably makes sense to have total visibility of the cluster for something like a policy change, which could potentially impact more than just a single vSAN host. Usual tasks such as creating new VM's and adding capacity are all still available and automatically tagged to the defined Default Storage Policies.

I have uploaded a short clip for those who may be interested. Hope this helps!