What if the most consumed host fails in VMware vSAN?

This could be a serious production hamper if you ignore the error of ‘What if the most consumed host fails in VMware vSAN cluster‘. We will explain on the Limits Health – After one additional host failure check in the vSAN Health Service and provides details on why it might report an error.

What does it mean for the vSAN Cluster Health?

Let suppose in your vSAN Cluster, There are five hosts available and one of your hosts fails. The resources under it such as Capacity and Cache disks will be unavailable to the vSAN cluster to use until it gets fixed. Meanwhile, vSAN will re-attempt to reprotect and rebuild the virtual machine objects on other available resources of four hosts. Now there would be reduced redundancy due to the host failure.

This health check simulates all the actions mentioned above. If the ESXi host with the most resources consumed fails, this health check calculates how much resources would be used from the remaining hosts in the cluster, and how much resources would still be available.

At the same time, the vSAN cluster will start throwing the warning message we are discussing.

For example, a user may enforce an operational business policy to have no less than 25% free disk space under normal conditions and no less than 15% free disk space after one failure. This check can be used to implement such a policy and to verify that this is indeed the case.

What can be done next?

If there are sufficient resources in your vSAN Cluster, There would not be an issue. You can ignore this warning supposing this as a routine vSAN cluster health check. But what if your cluster does not have that much of enough resources? Next time when any hosts fail, It would not be possible for vSAN to re-protect and rebuild virtual machines objects. And cluster will fail to remain active.

You should considering adding more ESXi to the cluster with higher capacity to avoid any further impact on your virtual environment.

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