When VMware vSAN was originally released, a two-node configuration was not supported. You needed three hosts for your hyper-converged infrastructure (HCI) to start with. It was only in later releases that VMware added this possibility. In this post, we'll have a look at the VMware vSAN 2 Node configuration and what's new in vSphere 7 with regard to vSAN configuration.

Just a reminder: a vSAN 2 Node Cluster needs a Witness Host. While in three-node (and more) clusters, VSAN Witness objects are stored and spread across all nodes within the cluster; however, the 2 Node configuration has the Witness objects stored only on the Witness Host. The two data hosts store the VM objects.

vSphere 7 and vSAN 7 have many improvements. The enhanced capacity reporting  in vSAN 7 includes new capabilities with a detailed view of storage consumption. vSAN 7 offers new possibilities for configuring native file services, NFS v3 and 4.1, to provide storage for Kubernetes or other applications running on vSphere 7. There's more, too.

While vSphere 6.7 introduced an assistant for the configuration of HA clusters and vSAN, vSphere 7 goes further to enable creating and configuring a distributed vSwitch during the process.

As you know, if you're a vSAN customer, you don't need a special license for DVSwitch, as this is included in you vSAN license. Even small customers with three to four hosts can benefit from DVSwitch in their vSAN 7 infrastructure.

The wizard walks you through the process of configuring vSAN 7. Note that you can clear the selection and configure the networking at a later stage.

Configure distributed vSwitch for VSAN

Configure distributed vSwitch for VSAN

Deployment of the Witness Host: Two possibilities ^

Case 1: The Witness Host is a virtual appliance with a special free license provided by VMware. However, the appliance is not able to run any VMs, as by its nature it is a VM too. It's only used to store the Witness objects that are needed to determine synchronization during split-brain situations.

Case 2: You can use a regular ESXi host, which can be configured to be a Witness Host.

The vSAN Witness Host has to be managed by the same vCenter Server that manages the vSAN cluster.

Network communication between nodes and the Witness Host ^

The vSAN Witness Host must also have connectivity between hosts and into each vSAN node. The important thing is that the Witness traffic is separated (a separate VMkernel interface must be tagged with witness traffic).

Witness Traffic Separation is actually a separation of the communication of vSAN data and vSAN metadata to the vSAN Witness Host. The communication to the vSAN Witness Host is done via a different VMkernel interface than the interface used to communicate between vSAN data nodes.

New in vSAN 7, there is automatic policy compliance for vSAN 2 Node deployments, where vSAN 7 keeps 2 Node deployments in policy compliance by automating operations on repair objects during witness replacement.

The deployment assistant allows you to choose which type of deployment you'd like to do. In our case, we're testing the two-host vSAN cluster.

Two Host vSAN Cluster

Two Host vSAN Cluster

The rest of the assistant is mostly the same, except for this screen. As you can see, vSAN Support Insight is ON by default.

vSAN Support Insight is ON by default

vSAN Support Insight is ON by default

vSAN Support collects some anonymous data to provide improved support experience and performance analytics.

When you call VMware Support, they'll be able to check and repair the problem faster because they will already have most of the data they will need. I should mention here that they collect only anonymous data, such as firmware and driver versions, to identify cluster-level issues.

vSAN 7 has a new capacity and monitoring screen, which also tracks history.

vSAN 7 capacity and monitoring screen

vSAN 7 capacity and monitoring screen

vSAN 7 also has a new pre-check data migration utility, enabling you to see what happens if one of the hosts is offline or in maintenance mode.

In our case, since we only have a two-node cluster, we cannot rebuild the components elsewhere if one node is down. That's the reason for the message.

vSAN 7 Pre check data migration

vSAN 7 Pre check data migration

Final words ^

VMware vSAN 7 provides a very quick configuration assistant that enables you to install and configure vSAN in a couple of minutes if all the requirements are met.

The vSAN 2 Node Cluster needs to have the Witness Host in a different location, usually in the main datacenter. The configuration that VMware recommends is to deploy several remote offices with 2 Node Clusters while hosting all the Witness Hosts (or appliances) within your main datacenter.

It makes more sense to host all Witness appliances on the shared storage of your main datacenter as you won't waste hardware by using the vSAN Witness Appliance, which is a VM.

Each 2 Node Cluster has its own Witness Host. All vSAN 2 Node Clusters are managed by a single vCenter Server.

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The best part is that you can use a direct connection between nodes in those remote offices. This means you'll have a data connection via direct connection cables, while the witness traffic travels over the management switch together with the management traffic back to the main datacenter where the solution is monitored and maintained. It saves a lot of money on switching equipment when managing dozens of remote offices with VSAN 7 2 Nodes.


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