Originally posted by Rawlinson Rivera, updated 5 JAN 17.
Since the initial release of Virtual SAN, customers have asked for a version of Virtual SAN for smaller environments, such as Remote Office / Branch Office (ROBO).
Today, Virtual SAN 6.1 introduces Virtual SAN 2 Node and Virtual SAN ROBO Licensing. Together, these provide the perfect solution for the demands of smaller ROBO environments and suitable use cases.
Virtual SAN ROBO Licensing
- A remote office or branch office is any remote physical location other than a primary data center
- Licensed in packs of 25 virtual machines
- A maximum of 25 virtual machines per remote office or branch office
- A single license may be spread across multiple locations
- Like vSphere ROBO Edition, there is no host count limitation
- No upgrade path to traditional vSAN licenses
Virtual SAN 2 Node is built on the foundation of Fault Domains
- In this case the required failure zones are based on three nodes (two physical nodes and witness host)
- The witness virtual appliance is uniquely designed with the sole purpose of providing cluster quorum services during failure events and to store witness objects and cluster metadata information
- The use of the witness virtual appliance eliminates the requirement of a third physical node
- Virtual SAN 2 Node is only capable of supporting a single failure within the cluster (FTT=1) due to the support of only three fault domains
A couple of facts about the Virtual SAN Witness Virtual Appliance:
- One witness virtual appliance is required per Virtual SAN 2 Node cluster
- The appliance does not contribute compute nor storage resources to the cluster
- It is not able to host virtual machines
- It is exclusively available and supported ONLY for Virtual SAN 2 Node/Virtual SAN Stretched Clusters
- The Witness Virtual Appliance is supported on an ESXi 5.5 installation or higher
- Another vSphere cluster in a central datacenter
- vCloud Air or vCloud Air Network
- A standalone ESXi host
New in Virtual SAN 6.1
Up until this release, Virtual SAN required a minimum of 3 nodes. This meant that customers had to have at least 3 Virtual SAN Nodes to use Virtual SAN. By removing the requirement for the third node, compute requirements are effectively 33% less. A Virtual SAN Witness Appliance is provided for free to perform the role of quorum for failure events and store Virtual SAN objects’ witness components and cluster metadata.
The Witness Virtual Appliance
From a configuration perspective, configuring a Virtual SAN 2 Node cluster is extremely simple as it is performed through a wizard within the vSphere Web Client. From a network perspective, the two Virtual SAN Cluster nodes are to be configured over a single layer 2 network with multicast enabled. They can also be configured over a layer 3 network as this is also supported, but in reality this would be a complex configuration that is not typically found in ROBO environments. The witness appliance network connectivity and communication requirements back to the centralized data center are listed below.
Witness Network Connectivity Requirements
- 1.5 Mbps connectivity
- 500 milliseconds latency RTT
- Layer 3 network connectivity without multicast to the nodes in the cluster
The Virtual SAN Witness Appliance is optimized to receive minimal amount of traffic when compared to scenarios with a traditional Virtual SAN cluster. At a steady state, there is barely any communication between the two nodes in the cluster and the witness. Read and write operations do not require any communication to the witness virtual appliance since the traffic to the witness virtual appliance is mostly limited to create, delete, reconfigure, and change policy operations.
Features, Cost, and Scale.
Removing the requirement for 3 nodes, along with per virtual machine pricing, reduces the overall cost of the solution from a CAPEX and OPEX perspective while allowing customers to reap the majority of the benefits of a Virtual SAN Cluster.
The table below lists the licensing package information as well as the features that are supported in Virtual SAN for ROBO.
If customers choose to add additional compute, they can easily scale to 3 or more nodes. The Virtual SAN ROBO License only limits the number of virtual machines per license. A maximum of 25 virtual machines may be used with a single Virtual SAN for ROBO license. This license can scale across multiple ROBO locations. When the number of virtual machines at a single location, or across locations exceeds a multiple of 25, additional licensing will be required.
How many licenses are needed?
In the illustration on the right, 3 remote sites have a total of 42 virtual machines deployed.
Because the total number of virtual machines across Site 1 and Site 2 are less than 25, a single Virtual SAN for ROBO license may be used.
Site 3 will require its own Virtual SAN for ROBO license.
Also notice that Site 3 has four hosts and not just two. This is because there is no host limit (beyond normal vSphere configuration maximums), but only a virtual machine limit.
Virtual SAN for ROBO licensing can grow as a business grows, 25 virtual machines at a time. Remember though, that there is no upgrade path from Virtual SAN for ROBO licensing to Virtual SAN Standard or Advanced licensing.
To see a recorded demonstration of the configuration procedure for the Virtual SAN cluster for ROBO, view VMware Virtual SAN 2 Node: Configuration Demonstration blog.
Update: Licensing has changed a bit for vSAN 6.5, including the introduction of vSAN ROBO Standard and vSAN ROBO Advanced licensing. These align with the feature set of vSAN Standard and vSAN Advanced licensing, while adhering to the 25 VM limit.