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Dell VxRail Architecture Overview


VMware vSAN ESA benefits to a VxRail stretched cluster with VMware vSAN

VMware vSAN ESA provides the following benefits to a stretched cluster:

  • The VMware vSAN ESA is designed with a focus on hardware optimization, allowing it to leverage high-performance NVMe devices and architectural changes to remove the limitations of disk groups.
  • In contrast to the VMware vSAN OSA, the VMware vSAN ESA employs a different data preparation method. It consolidates numerous small writes in memory before writing the data to disk.
  • The VMware vSAN ESA achieves a more uniform data delivery across the Interswitch Links (ISL), resulting in improved performance by reducing the number of smaller I/O operations and using larger ones.
  • The VMware vSAN ESA compresses data before transmitting a write across the ISL. This reduces the amount of data that is sent between the two sites for the same workloads, alleviating write latency that was previously caused by ISL contention. As a result, the effective write throughput across the ISL increases, comparable to enhancing the bandwidth of the ISL, thereby enhancing performance consistency of VMs in a stretched cluster.

Stretched cluster nodes

Stretched clusters are deployed across two sites in an active configuration. An identical number of VMware ESXi hosts are recommended at each site. VxRail supports an unbalanced configuration with the use of Site Affinity Rules.

Stretched cluster deployment options

Plan the VxRail vSAN stretched cluster deployment before installation. Depending on the number of nodes in the VxRail cluster, do one of the following:

  • Deploy up to 16 nodes on initial deployment.
  • Initially deploy the minimum number of nodes per site and then scale out additional nodes either at installation or during the VxRail vSAN stretched cluster life cycle.

Stretched cluster consideration

The following are the requirements to implement VMware vSAN stretched clusters in a VxRail cluster running VxRail 7.0 or later versions:

  • The VxRail cluster must be deployed across two physical sites in an active configuration.
  • The minimum supported configuration is 1+1+1 (2 nodes +1 witness).
  • The maximum supported configuration is 20+20+1 (40 nodes plus + VMware vSAN 1 witness).
  • A witness host must be installed on a separate site as part of the installation engagement. The witness must be running the same version as the VMware vSphere for version compatibility.

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