Cluster Load Balancing.
You might think, Tim,
why are we looking at load balancing from a different perspective?
Isn't this what failover clustering is all about?
Well, kind of.
I mean, it depends is the classic IT consultant's answer.
Recall that failover clustering itself is a way to do high availability,
and yes, as we saw,
there are some features now and then that crop up that help with load balancing,
that automatic client rebalancing feature that's part of SOFS as an example,
but the exam wants you to understand some other features.
For instance,
there is a property called auto balancer level that you can set on your
cluster that optimizes cluster node utilizations.
Again,
this is where clustered VMs may be moved due to patching
and also to support that idea of preventing an unbalanced
cluster where one cluster node,
and this is different from the SOFS automatic client rebalancing,
by the way, this failover clustering VM load balancing totally separate property,
but it has some overlap in functionality.
We're looking to make sure that we can support our cluster nodes so that they
don't wind up getting oversaturated hosting too many VMs.
How does the failover cluster implement this built‑in VM load balancing feature?
Well there are some heuristics that play, some metrics.
Basically, the cluster is looking at the host's memory pressure,
as well as their CPU utilization.
And then from a configuration standpoint,
you can use PowerShell to set the AutoBalancerLevel property.
The default setting is 1 in which the cluster will live
migrate a VM to a different host when the host is greater
than 80% utilized with CPU and RAM.
You can also switch that.
There are a couple other legal values here where you can move
VMs when the host is 70% or more utilized,
and then there is an option 3 that'll live migrate your VMs when the host is
just greater than 5% above the aggregate cluster average.
So you would set this,
you'd either leave the property at the default or change it depending upon how
aggressive you want the cluster to be in protecting nodes.
So that is a property you should know for your exam,
very useful when you're doing highly available virtual machines in your failover cluster.