One nice new advantage of using Windows Server 2022 is the ability to set up a cluster on systems not part of the same domain. Windows Server 2022 allows you to set up a cluster without using Active Directory dependencies. You can create clusters in the following situations:
Single- Domain Cluster All nodes in a cluster are part of the same domain.
Multidomain Cluster Nodes in a cluster are part of a different domain.
Workgroup Cluster Nodes are member servers and part of a workgroup.
Site- Aware, Stretched, or Geographically Dispersed
Clusters (Geoclustering)
One nice advantage of Windows Server 2022 clustering is that you can set up site- aware failover clusters. Using site- aware clustering, you can expand clustered nodes to different geographic locations (sites). Site- aware failover clusters allow you to set up clusters in remote locations for failover, placement policies, Cross-S ite Heartbeating, and quorum placement.
One of the issues with previous clusters was the heartbeat. The cluster heartbeat is a signal sent between servers so that they know the machines are up and running. Servers send heartbeats, and if after five nonresponsive heartbeats, the cluster assumes that the node was offline. So, if you had nodes in remote locations, the heartbeats would not get the response they needed.
But now Windows Server 2022 includes Cross- Site Heartbeating, which allows you to set up delays so that remote nodes can answer the heartbeat in time. Use the following two PowerShell commands to specify the delay necessary for Cross- Site Heartbeating:
(Get- Cluster).CrossSiteDelay = <value>
(Get- Cluster).CrossSiteThreshold = <value>
The first PowerShell command (CrossSiteDelay) is what is used to set the amount of time between each heartbeat sent to nodes. This value is done in milliseconds (the default is 1000).
The second PowerShell command (CrossSiteThreshold) is the value that you set for the number of missed heartbeats (the default is 20) before the node is considered offline.
One issue you may face is if you have multiple sites or if the cluster is geographically dispersed. If the failover cluster does not have a shared common disk, data replication between nodes might not pass the cluster validation “storage” tests.
Setting up a cluster in a site- aware, stretched, or geocluster (these terms can be used interchangeably) configuration is a common practice. As long as the cluster solution does not require external storage to fail over, it will not need to pass the storage test to function properly.
Cluster Quorum
When a group of people set out to accomplish a single task or goal, a method for settling disagreements and for making decisions is required. In the case of a cluster, the goal is to provide a highly available service in spite of failures. When a problem occurs and a cluster node loses communication with the other nodes because of a network error, the functioning nodes are supposed to try to bring the redundant service back online.
How, though, is it determined which node should bring the clustered service back online?
If all the nodes are functional despite the network communications issue, each one might try. Just like a group of people with their own ideas, a method must be put in place to determine which idea, or node, to grant control of the cluster. Windows Server 2022 failover clustering, like other clustering technologies, requires that a quorum exist between the cluster nodes before a cluster becomes available.
A quorum is a consensus of the status of each of the nodes in the cluster. Quorum must be achieved in order for a clustered application to come online by obtaining a majority of the votes available (see Figure 13.12). Windows Server 2022 has four models, or methods, for determining quorum and for adjusting the number and types of votes available:
■ Node majority (no witness)
■ Node majority with witness (disk or file share)
■ Node and file share majority
■ No majority (disk witness only)
FIGURE 13.12 Majority needed
When a majority of the nodes are communicating, the cluster is functional.
When a majority of the nodes are not communicating, the cluster stops.
Witness Configuration
Most administrators follow some basic rules. For example, when you configure a quorum, the voting components in the cluster should be an odd number. For example, if I set up a quorum for five elements and I lose one element, I continue to work. If I lose two elements, I continue to work. If I lose three elements, the cluster stops—a s soon as it hits half plus 1, the cluster stops. This works well with an odd number.
If the cluster contains an even number of voting elements, you should then configure a disk witness or a file share witness. The advantage of using a witness (disk or file share) is that the cluster will continue to run even if half of the cluster nodes simultaneously go down or are disconnected. Configuring a disk witness is possible only if the storage vendor supports read- write access from all sites to the replicated storage.
One of the advantages of Windows Server 2022 is the advanced quorum configuration option. This option allows you to assign or remove quorum votes on a per-n ode basis. You now have the ability to remove votes from nodes in certain configurations. For example, if your organization uses a site- aware cluster, you may choose to remove votes from the nodes in the backup site. This way, those backup nodes would not affect your quorum calculations.
There are different ways that you can set up quorum witnesses. Here are some of the options that you can choose from:
Configuring a Disk Witness Choose the quorum disk witness if all nodes can see the disks. To set up this disk witness, the cluster must be able to see the dedicated LUN. The LUN needs to store a copy of the cluster database, and it’s most useful for clusters that are using shared storage. The following list is just some of the requirements when setting up a disk witness:
■ The LUN needs to be at least 512 MB minimum.
■ The disk must be dedicated to cluster use only.
■ Must pass disk storage validation tests.
■ The disk can’t be used as a Cluster Shared Volume (CSV).
■ You must use a single volume for Basic disks.
■ No drive letter is needed.
■ The drive must be formatted using NTFS or ReFS.
■ Can be used with hardware RAID.
■ Should not be used with antivirus or backup software.
Configuring a File Share Witness You should use the file share witness when you need to think about multisite disaster recovery and the file server must be using the SMB file share.
The following list is just some of the requirements when setting up a file share witness:
■ Minimum of 5 MB of free space.
■ File share must be dedicated to the cluster and not used to store user data or application data.
Configuring a Cloud Witness The Windows Server 2022 cloud witness is a new type of failover cluster quorum witness that leverages Azure as the intercession point. The cloud witness gets a vote just like any other quorum witness. You can set up the cloud witness as a quorum witness using the Configure A Cluster Quorum Wizard.
Dynamic Quorum Management
Windows Server 2022 provides dynamic quorum management, which automatically manages the vote assignment to nodes. With this feature enabled, votes are automatically added or removed from nodes when that node either joins or leaves a cluster. In Windows Server 2022, dynamic quorum management is enabled by default.
