vSAN 2-Node Configuration on VxRail

VMware vSAN 2-Node Cluster is a configuration implemented in environments where a minimal configuration is a key requirement, typically in Remote Office and Branch Office (ROBO). A VMware vSAN 2-Node Cluster on VxRail consists of a cluster with two directly connected VxRail E560 or E560F nodes, and a Witness Host deployed as a Virtual Appliance. The VxRail cluster is deployed and managed by VxRail Manager and VMware vCenter Server.

A vSAN 2-Node configuration is very similar to a Stretched Cluster configuration. The Witness Host is the component that provides quorum for the two data nodes in the event of a failure. This vSAN 2-Node configuration includes two deployment architecture, i.e. the vCenter server and Witness host can locate in a main datacenter or same location. The following are the two options of deploying vCenter and Witness.

Remark: RTT between Witness and data nodes up to 500ms. Bandwidth of at least 1.5Mbps. Minimum VxRail software version is 4.7.100

2-Node Licensing Options for vSAN

Option A: vSAN ROBO license

  • Per-VM licensing model (Standard, Enterprise, Advanced editions)
  • Support total of 25 powered-on VMs in single location or across multiple locations

Option B: regular vSAN license

  • Deployments running more than 25 VMs
  • Per-socket licensing model

vSAN 2-node basics

  • Both nodes must be in a single physical location
  • Only supports PFTT=1, mirroring (VM objects are mirrored across two nodes, FTT=1)
  • Witness host required as the tiebreaker
  • 3 fault domains (Witness host included)
  • Can use either normal per-socket vSAN licenses or the per-VM vSAN ROBO licenses

Witness host

  • Virtual appliance running ESXi (multiple sizes depending on VM count)
  • Receives Witness traffic from the two nodes
  • must run outside of cluster and requires Witness traffic separation
  • Can run on a host within the same rack, but not in the 2-node cluster

vCenter and Witness host on separate server or cluster at a same site

  • Ports 1 and 2 for HA for ESXi management, VM network, and Witness traffic
  • Ports 3 and 4 for vSAN and vMotion directly connected to each other
  • Separate Witness management traffic from vSAN traffic
  • vCenter server cannot be installed in the same cluster

 

vCenter and Witness are locate in HQ datacenter.

6 comments

    1. Only supports PFTT=1, mirroring (VM objects are mirrored across two nodes, FTT=1). The VM is still running in health if the impact of failure of one node. Best practice to run less than 50% of a nodes resource load, so a single node can bear full cluster load in case of a node failure.

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