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.

The 2-node cluster provides the following features:

• 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. The 2-node cluster meets the needs of environments that have space, budget, and IT personnel constraints.
• A 2-node cluster configuration is like 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.

From VxRail 7.0.410, the VMware vCenter Server for a 2-node cluster can be installed as part of the day 1 installation. Except for the VD-4000 A witness host external to the 2-node cluster must be provided to complete the first-run installation.

With the introduction of the VD-4000 VxRail, the optional VD-4000w sled can be added to the chassis. Where the VD-4000 is used as a single cluster of 2 VD-4510c or VD-4520c compute nodes with a VD-4000w installed in the same chassis, the day 1 installation includes deployment of the vSAN witness appliance to the sled. The witness host (vSAN witness appliance) and the VD-4000w are fully managed by the VxRail manager and dedicated to that cluster. The sled card is installed in the chassis slot. The witness sled is smaller than the node sleds and has a smaller slot that is reserved for this purpose.

A 2-node cluster maintains the same high-availability characteristics as a regular cluster. Each physical node is configured as a VMware vSAN fault domain, with a copy of all VMware vSAN objects (a component) on each ESXi (FD). If a node or device fails, VMs remain accessible through the replica and witness components.