What advantages do Windows Server cluster sets offer?

How cluster sets increase resiliency

The goal of cluster sets is to support scale-out -- rather than scale-up -- capability. Consider a typical cluster: If the storage or memory resources start to run low, the administrator must scale up the cluster by adding more resources.

However, that isn't always a simple proposition. For example, adding storage may affect rebuild times, and it may be impossible to add more memory on hosts with full dual in-line memory module slots. Adding more nodes or redesigning an entirely new cluster is often expensive and undesirable.

Windows Server cluster sets combine multiple clusters into a fabric, so member clusters can share resources, such as storage and memory. This scale-out behavior reduces costs and adds flexibility to clustering without compromising the resiliency of the individual member clusters.

For example, a cluster that uses storage technology such as Storage Spaces Direct can survive the loss of two nodes. Thus, a cluster with four nodes will fail if three nodes fail. Yet, a cluster with eight nodes will also fail if three nodes fail. By comparison, in Windows Server 2019's cluster sets, two clusters with four nodes each can still function if the same three nodes crash.

Combining clusters into a greater fabric doesn't necessarily improve the hardiness of individual member clusters, but establishing a fabric of clusters and sharing resources can provide better resilience across the overall fabric. The fault boundary does not extend beyond the member cluster where the fault occurs.

Cluster sets break previous hardware restrictions

Windows Server cluster sets combine clusters into a common logical fabric that can span facilities and geographic regions.

At a low level, cluster sets can ease the limitations posed by cluster hardware requirements. For example, typical clusters require closely matched processor capabilities. However, those requirements do not extend across the entire fabric.

It is possible to create one cluster of older hardware and another cluster of newer hardware, and then join both clusters using Windows Server 2019 cluster sets. This can help organizations looking to repurpose or extend the lifecycle of existing hardware, while mitigating the investment in new hardware.

At a higher level, a cluster set can include clusters located in different physical areas to implement cloud-like availability sets or availability zones.

Cluster sets ease VM management

Windows Server cluster sets can simplify cluster management. Once an administrator establishes the cluster fabric with a unified namespace, they can use centralized cluster management to select the cluster and node best suited to handle a new VM based on the requirements and each cluster's available resources. Conversely, admins can tag VMs with specific needs to utilize predetermined clusters.

IT pros can move VMs between member clusters, while the individual cluster will determine which node should receive the VM. This behavior can benefit administrators with tasks such as transferring all VMs off an aged cluster before decommissioning it.