Cluster‑Aware Updating, or CAU for short. It's not going to be too
long in your life as a Windows Server failover cluster
administrator that you're going to have questions like, wait a
minute, what about Microsoft updates?
How can we apply and patch our cluster nodes without
interrupting the failover cluster? Well,
cluster‑aware updating, or CAU, Microsoft already thought of this, it's a
technology that's part of the failover clustering feature that maintains
cluster high availability during the Microsoft Update patching cycle. The
plug‑in model is actually extensible, so you can go beyond there if you
want to or you need to.
So, the question of uh‑oh, would I not be able to
use my own patching solution? No, that's not necessarily true.
You may very well,
especially, of course, if you're using WSUS. You can integrate that
patch management strategy with your failover clusters.
Now there's two ways to do updating runs on your cluster using CAU.
One would be, of course, manually triggering an update, and then
there's configuring self‑updating via schedule.
Let's have a look at the cluster‑aware updating update
workflow. What happens when CAU runs is it's going to pick
a node, hopefully it makes sense.
You have to start somewhere. That node will go into
maintenance mode. It will become paused, and of course,
that's basically a failover event.
So CAU will move any clustered roles for which that first node is active
to another node. And we'll learn formally in this lesson a little bit
later about the concept of the preferred owner. So you can make sure
that if you have a designated second host that you want to nominate for
those clustered roles,
you can do that. Course three is installing the updates from
Microsoft Update or WCUS. Restart is almost a given most of the
time, unless it's a very slight update.
The CAU process can handle automatically restarting and resuming the
update process. Once the updates are complete,
CAU will then unpause the node,
restore clustered roles back to that node, and then move on to
the next one until the process is finished.
This is some nice engineering.
It's basically a self‑contained, self‑operating rolling patch management
solution for your Windows Server failover clusters.
Cluster‑aware updating is actually a separate product
from failover clustering specifically.
And what I mean by that is you can see on this slide and you'll see in
the demo, there's a separate user interface for cluster‑aware updating
where you can connect to your clusters.
If you have more than one,
you can do some basic reporting. You can look at what updates are needed
for your cluster and so on and so forth, so you really can manage the
entire service graphically here if you want to.
However,
in 21st century IT and with DevOps, I would suggest that you
automate and use programmatic methods. And here, we see a
screenshot of a PowerShell console.
We see that there's a separate PowerShell module called
ClusterAwareUpdating. It contains 20 or so cmdlets.
Here's an example of using Invoke‑CauRun to set up a
scheduled self‑updating run for the cluster.
So here we're doing ‑ClusterName. That makes sense.
That's the client access point for the cluster itself.
We specify which plugin we want to use. And then there's some additional
logic in terms of parameters how you want that to work.
And again,
it's essentially an equivalent process, whether you're configuring
self‑updating programmatically with Windows PowerShell versus using the GUI. It's largely a preference.