While VMware ESXi is a powerful platform in a standalone host configuration (single ESXi host), the true power, high availability, scalability, resource management, and resiliency of the platform is only unlocked in a vSphere ESXi cluster. What is the difference in a standalone ESXi host and a vSphere cluster?
In a VMware ESXi cluster configuration, multiple ESXi hosts provide compute, memory, and network resources to the cluster environment as a whole, as well as protect cluster-housed VMs against physical server failures. This is accomplished by using a VMware vCenter Server (a requirement to create a VMware ESXi cluster). Once created, a vSphere cluster enables “cluster only” features such as HA (high availability) and DRS (distributed resource scheduler). Each of these features contributes to the tolerance of the VMware cluster withstanding failures as well as distributing resources across the VMware ESXi hosts. We will take a look at both of these in detail in upcoming posts. First though, let us take a look at the process of creating a VMware ESXi Cluster.
Creating a VMware ESXi Cluster
The configuration process for creating a VMware vSphere ESXi cluster is fairly straightforward. The main requirement is that you have a VMware vCenter Server up and running as well as have network connectivity to the intended ESXi hosts that are to join the cluster.
Let’s take a look at the steps to create a cluster once we have connected to the Web UI of our vCenter Server.
Right click on your vCenter server in the Web UI and choose New Datacenter. The datacenter object contains all the different types of objects needed to do work in the virtual infrastructure – hosts, VMs, networks, datastores, etc.
Next, we assign a Datacenter name:
How to Create a New Cluster
Once the datacenter is created, we can choose to create a New cluster.
We assign a cluster name.
Once the cluster object is added, we can Add Hosts to the Cluster object. Once we add a host to a cluster, the host’s resources become part of the cluster’s resources. The cluster manages the resources of all hosts.
The Add Host wizard begins and we enter the name or IP address of the host to add to the cluster.
Provide the credentials to access the host.
You may receive a certificate alert. Simply click Yes to continue connecting. This is a common warning with self-signed certificates present on the hosts by default. We can safely ignore this warning.
The Host summary screen shows us any VMs that are present on the host if any.
We have the option to select the license we want to use on the host. You can simply choose the evaluation license to continue with the trial license which is good for 60 days.
Lockdown mode prevents remote users from logging into the host directly. This option is available for a more secure posture with the ESXi hosts. This can be enabled later as well.
Finally, we are ready to add the host. We will continue this process for all the hosts we wish to join to the cluster.
As you can now see, we have a datacenter, cluster, and our two ESXi hosts joined to the cluster.
To unlock the true potential of a VMware ESXi hypervisor environment, utilizing the VMware vSphere cluster functionality is key. Running VMware ESXi in the cluster configuration with VMware vCenter server allows you to utilize the enterprise datacenter VMware vSphere technologies including HA (high availability) and DRS (distributed resource scheduler). Both of these technologies contribute to the tolerance of the VMware cluster withstanding failures as well as distributing resources across the VMware ESXi hosts. In the standalone VMware ESXi configuration, this is not possible. Next, we will take a look at VMware DRS.