Now, what's this about Cluster‑Aware Updating, or CAU?
Well,
this is a built‑in capability of Windows Server failover
clustering that automates Microsoft software updates without
sacrificing high availability.
It is a separate server feature that you'll need to install,
it has a separate user interface as a matter of fact,
separate PowerShell module.
And here, we're looking at Microsoft updates,
and you can either run Cluster‑Aware Updating runs on
your cluster manually and interactively,
or, perhaps more commonly,
you'll schedule the cluster to do self‑updating runs on its own.
One thing that's neat about Cluster‑Aware Updating,
among many things actually, is that it's a hands‑off process.
In other words, it automates,
patching your servers from either Microsoft update or you
could use Windows Server Update Service.
And it automates draining clustered roles from each node,
updating the node, taking it offline, putting it in maintenance mode,
patching, rebooting,
and then failing back the clustered roles that that
machine should host or be primary for.
It's a rolling update and nice way to keep your cluster hosts secure.
What is a cluster set?
Well, this is a more recent addition to Windows Server failover clustering.
It is a way to create a much larger topology for
your Windows cluster environment.
In the previous module,
we spent just a small amount of time looking at the stretch cluster,
where you have a single cluster that has replicated
shared storage across multiple sites,
and the nodes are all part of the same logical cluster.
Well, cluster set is another layer of abstraction.
As you can see on the top of the screen,
you've got a Management cluster,
and then you join one or more totally separate member clusters to the set.
This uses the Scale‑Out File Server namespace as a way to logically connect
or logically have a pathway across this topology here.
And this gives us potentially some really big benefits for businesses
that may or may not be comprising of multiple sites,
but at the least,
you want to provide as many layers of redundancy and fault tolerance as you can.
So again, this is another image of a cluster set, a logical image from the docs.
You can see my attribution URL in the upper right.
That when you define your cluster set with PowerShell,
you're using the Scale‑Out File Server role,
you've got your management cluster, and then you've got your member clusters.
And the idea here is that you then have much bigger
portability of your services,
specifically cluster set is intended for highly available virtual machines.
So you may have a VM that's running in the management cluster,
and then a failover event needs to take place.
It could not only failover to another node within the management cluster,
but it could actually failover to any of your member clusters as well.
Another thing that you do with the cluster set is that you
define fault domains and availability sets.
Now, you might be thinking, if you've used high availability in Azure,
particularly with virtual machines, you might think,
wait a minute now, I know what an availability set is and a fault domain.
In Azure terminology an availability set is two or more
replica VMs that you put in this container,
essentially,
that tells Microsoft to separate those VMs to make sure
that they're on separate server racks, those are fault domains,
and separate hosts, those are update domains,
to ensure availability of your service.
Well notice that you've got a similar motif here,
where in this topology,
it looks like Member Cluster 1 and 2 are logically
associated with Fault Domain A.
So, these could be clusters and nodes that are in the same datacenter,
the same rack, the same site,
and then we have Cluster 3 and Cluster 4 as separate fault domains.
So you can, again, just get a wider picture of your cluster topology.
I hope that makes some semblance of sense.
This is another feature that could be a course unto itself.
It's a gigantic subject.
I've just explained the surface‑level points that you
should keep in mind about cluster sets.
So on the exam, if AZ‑104 were to ask you a question like,
you're a hybrid cloud administrator and you need to
put together a logical layer, a high‑availability layer,
on multiple failover clusters across multiple sites.
The correct answer would be to use, say,
PowerShell to define a cluster set in which you've got one management cluster,
one or more member clusters, SOFS namespace that goes across the entire set, and then you aggregate those clusters into fault domains.