A cluster set is a group of multiple failover clusters that are clustered together. You can increase the number of server nodes in a single software- defined datacenter (SDDC) cloud by orders of magnitude by configuring cluster sets.
Benefits of Cluster Sets
There are a number of benefits of cluster sets, such as the following:
■ Support is increased on the SDDC cloud scale for running highly available VMs by joining several smaller clusters into a single larger one. This allows you to migrate VMs across the cluster set.
■ Increases resiliency by having multiple clusters in a cluster set will give you better resiliency than if you were using a single cluster in case a node goes down.
■ You can manage the failover cluster life cycle, including onboarding and retiring clusters, without affecting tenant VM availability.
■ Flexibility of the VMs across individual clusters and offers a unified storage namespace.
■ Can change the compute- to- storage workload ratio in your hyper-c onverged environment.
■ Live migration of VMs between clusters.
Requirements and Limitations of Cluster Sets
There are some requirements and limitations for using cluster sets:
■ All member clusters must be in the same Active Directory (AD) forest.
■ Virtual machines can’t be live-m igrated between different operating systems, so member servers must run the same operating system version.
■ For live migration, identical processor hardware is needed for all member servers between clusters to occur. If not, then you must select CPU Processor Compatibility in the virtual machines’ settings.
■ Cluster set VMs must be manually live-m igrated across clusters. They cannot fail over automatically.
■ Storage Replica must be used between member clusters for storage resiliency in case of cluster failures.
■ Storage Spaces Direct doesn’t function across member clusters. Storage Spaces Direct applies to a single cluster, with each cluster having its own storage pool.
Cluster Set Architecture
There are a number of elements within a cluster set:
Management Cluster This hosts the highly available management plane and the namespace referral Scale- Out File Server (SOFS) for the cluster set.
Cluster Set Namespace Referral SOFS This is a namespace for the cluster set. It is used with an SOFS server role running on the management cluster.
Cluster Set Master The cluster set master (CS- Master) resource is highly available and resilient to individual member cluster or management cluster node failures. The CS- Master handles and coordinates the communication between member clusters.
Member Cluster Runs the VM and Storage Spaces Direct workloads.
Cluster Set Worker The cluster set worker (CS- Worker) responds to requests by the CS- Master, including VM placement and doing resource inventory. There is one CS- Worker instance per member cluster.
Fault Domain A group of hardware and software that could fail together. Fault domain boundaries are based on datacenter topology, networking architecture, and other considerations.
Availability Set Used to configure the redundancy of clustered workloads across fault domains by grouping and deploying workloads.
Creating Cluster Sets
In order to create cluster sets, you must first configure a management client and install the failover cluster tools on the server. Then, the member clusters need to be created. I discussed creating failover clusters earlier in the chapter. You should create a separate management cluster that will oversee the member clusters.
Once the failover clusters are created, you will then run a series of PowerShell commands to create the cluster set. If you wish to see an example of creating a cluster set step by step, please visit the Microsoft website at https://learn.microsoft.com/en- us/ windows- server/failover- clustering/cluster- set#create- a- cluster- set.
Here are some of the PowerShell commands that you can use to create a new cluster set:
New- ClusterSet Creates a new cluster set
Add- ClusterSetMember Adds members to a cluster set
Get- ClusterSetMember Lists the nodes and properties of each node
Get- ClusterSet Lists the member clusters and management cluster nodes
Get- ClusterSetNode Lists all the nodes for the cluster set
Get- SmbShare Lists the SMB shares on the cluster set
Get- ClusterSetog Lists information pertaining to one or more nodes in a cluster set
Azure Stack HCI
Azure Stack HCI is a hyperconverged infrastructure (HCI) cluster solution that hosts virtualized Windows and Linux workloads and their storage in a hybrid environment. It merges your on- premises infrastructure with Azure cloud services. Azure Stack HCI is delivered as an Azure service and billed to an Azure subscription. It is priced on a per-c ore basis on your on- premises server. When you first download the Azure Stack HCI, you get a free 60-d ay trial. After the trial, the price is $10 per physical core per month. To download the Azure Stack HCI software, go to Microsoft’s website at https://azure.microsoft.com/ en- us/contact/azure- stack- hci.
Azure Stack HCI is intended to be used as a virtualization host, so most apps and server roles must run inside of VMs. You can also manage your clusters using the Windows Admin Center and PowerShell. Each Azure Stack HCI cluster consists of between 1 and 16 physical validated servers.
By using Azure Stack HCI and Windows Admin Center, you can create a hyperconverged cluster that uses Storage Spaces Direct with the option to stretch the cluster across sites and use automatic failover. For clusters stretched across sites you need at least four severs (two in each site) with at least one 1 Gb connection between the sites (a 25 Gb RDMA connection is preferred).
Create a Cluster using the Windows Admin Center
To create a simple two- node, single- site cluster, perform the following steps:
- In Windows Admin Center, under All Connections, select Add.
- In the Add Resources panel, under Windows Server Cluster, select Create New.
- Under Choose Cluster Type, select Azure Stack HCI.
- Under Select Server Locations, select All Servers In One Site.
- Click Create. You will now see the Create Cluster Wizard. If the Credential Security Service Provider (CredSSP) pop- up appears, select Yes to temporarily enable it.
The Create Cluster Wizard has five sections, each with its own steps:
Get Started This section allows you to check for any prerequisites, add servers, join a domain, install required features and updates, and restart the servers.
Networking This section will verify that the correct networking adapters are enabled and will disable any unused adapters. From here you can select management adapters, set up a virtual switch configuration, and define the network by supplying IP addresses.
Clustering This section will validate that the servers have a consistent configuration and are suitable for clustering, and then you will create the actual cluster.
Storage This section will clean and check drives, validate storage, and enable Storage Spaces Direct.
SDN This section is optional and you will only be using it if you set up software- defined networking (SDN) for your clusters.
To add and connect to an Azure Stack HCI cluster using the Windows Admin Center, you can add a cluster to manage from the main overview page by performing the following steps:
- Click + Add under All Connections.
- Choose Add A Windows Server Cluster.
- Type the name of the cluster you want to manage and click Add. The cluster will be added to the connection list on the overview page.
- Under All Connections, click the name of the cluster you just added. Windows Admin Center will start Cluster Manager and take you directly to the Windows Admin Center dashboard for that cluster.
