Dell VxRail Architecture Overview

VxRail 2-node cluster with VMware vSAN

A VxRail 2-node cluster with VMware vSAN consists of a minimal configuration of two data nodes and a witness virtual appliance. VxRail 4.7.100 and later versions support 2-node cluster direct-connect configurations.

The 2-node cluster provides the following features:

• VxRail 4.7.410 and later versions support switch configuration.
• The 2-node cluster can be deployed anywhere.
• A single VMware vCenter Server instance can manage many 2-node clusters.
• The 2-node cluster provides the same functional benefits of VMware vSphere and VMware vSAN.
• The 2-node cluster enables efficient centralized management with reduced hardware and software costs, while meeting the needs of environments that have space, budget, and IT personnel constraints.
• A 2-node cluster configuration is similar to a stretched cluster configuration. If a failure occurs, the witness host is the component that provides quorum for the two data nodes. The requirement for one witness per cluster applies.

Unlike in a stretched cluster, the VMware vCenter Server and the witness host are usually in a main data center. The two VMware vSAN data nodes are typically deployed in a remote location, even though the witness host can be deployed at the same site as the data nodes. The most common deployment for multiple 2-node clusters is to use a shared witness that is hosted in the same management cluster as the VMware vCenter Server. This deployment optimizes the infrastructure cost by sharing the VMware vSphere licenses and the management hosts.

From VxRail 7.0.410, the VMware vCenter Server for a 2-node cluster can be installed as part of the Day 1 bring-up operation. Install the witness externally from the 2-node cluster. With the VD-4000 and VxRail 7.0.420, you can purchase a sled card that can run the witness if two VD-4000 are being deployed as a 2-node cluster. The witness running on the sled card is not shareable with other 2-node clusters. The sled card is installed in chassis slots. The witness sled is smaller than the node sleds, and therefore has a smaller slot reserved for this purpose. A 2-node configuration maintains the same high-availability characteristics as a regular cluster. Each physical node is configured as a VMware vSAN Fault Domain, which means that the VMs can have one copy of data on each Fault Domain. If a node or a device fails, the VM remains accessible through the alternate replica and witness components.