There are many advantages to virtualizing vCenter Server over installing it on physical devices; these have been blogged about already. VMware best practice also recommends the deployment of vCenter Server as a virtual machine and to use vSphere High Availability (HA) to provide this functionality. The typical scenario is to place vCenter Server in a vSphere HA cluster. HA will protect vCenter Server just like any other virtual machine. If the ESXi server that is running vCenter Server goes down, HA will kick-in and power on this VM from the shared storage on another HA cluster member host. In this blog, we will show the downtime of vCenter Server in this scenario with experiments that simulate a production deployment.
We performed our experiments with a vCenter Server VM deployed in an HA-enabled cluster with vCenter Server itself managing an inventory of 64 hosts and 6,000 VMs. The experiment shows that in case the ESXi server which hosts vCenter Server fails, vCenter Server will be powered on by another host in the cluster as expected in the HA scenario. After vCenter Server is powered on, it takes time to boot up into full function, and 64 hosts/6,000 VMs will be presented in the inventory when the administrator is able to log into the vSphere Web Client again. In our experiments, the whole procedure from failure to vCenter Server administrator being able to log into the vSphere Web Client took about 7 minutes and 40 seconds, with most of the time spent booting up vCenter Server into full function. During vCenter Server downtime, customers will still be able to access their VMs; only the vCenter Server administrator is impacted.
In the following sections, we describe our experiments and numbers.
EXPERIMENTAL DEPLOYMENT SCENARIOS
We created the scenario of vCenter Server in an HA-enabled cluster environment. We used a host simulator to simulate the 64 hosts/6,000 VMs inventory for vCenter Server. The deployment is shown in figure 1, below.