Specific vSAN configurations, such as a stretched cluster, require a witness host. Instead of using a dedicated physical ESXi host as a witness host, you can deploy the vSAN witness appliance. The appliance is a preconfigured virtual machine that runs ESXi and is distributed as an OVA file.
Unlike a general purpose ESXi host, the witness appliance does not run virtual machines. Its only purpose is to serve as a vSAN witness.
The workflow to deploy and configure the vSAN witness appliance includes this process.
- Tiny supports up to 750 components (10 VMs or fewer).
- Medium supports up to 21,833 components (500 VMs). As a shared witness, the Medium witness appliance supports up to 21,000 components and up to 21 vSAN two-node clusters.
- Large supports up to 64,000 components (more than 500 VMs). As a shared witness, the Large witness appliance supports up to 24,000 components and up to 24 vSAN two-node clusters.
- Extra Large supports up to 64,000 components (more than 500 VMs). As a shared witness, the Extra Large witness appliance supports up to 64,000 components and up to 64 vSAN two-node clusters.
You also must select a datastore for the vSAN witness appliance. The witness appliance must use a different datastore than the vSAN stretched cluster datastore.
- Download the appliance from the VMware website.
- Deploy the appliance to a vSAN host or cluster. For more information, see Deploying OVF Templates in the vSphere Virtual Machine Administration documentation.
- Configure the vSAN network on the witness appliance.
- Configure the management network on the witness appliance.
- Add the appliance to vCenter Server as a witness ESXi host. Make sure to configure the vSAN VMkernel interface on the host.