file share, but many environments do not have the infrastructure to utilize SMB 3 at a
datacenter level or already have large SAN investments.
As you can see, some of the features of clustering for Hyper-V are now available
outside of a cluster at some level, but not with the same level of efficiency and
typically only in planned scenarios. Additionally, a cluster provides a boundary of host
membership, which can be used for other purposes, such as virtual machine
rebalancing, placement optimization, and even automation processes such as cluster
patching. I cover migration, CSV, and the other technologies briefly mentioned in
detail later in this chapter.
Clustering brings high availability solutions to unplanned scenarios, but it also brings
some other features to virtual machine workloads. It is because of some of these
features that occasionally you will see a single-node cluster of virtual machines.
Hyper-V has great availability features, but they are no substitute for clustering to
maintain availability during unplanned outages and to simplify maintenance options,
so don’t overlook clustering.
Service Monitoring
Failover Clustering provides high availability to the virtual machine in the event of a
host failure, but it does not provide protection or assistance if a service within the
virtual machine fails. Clustering is strictly making sure that the virtual machine is
running; it offers no assistance to the operating system running within the virtual
machine.
Windows Server 2012 clustering changed this by introducing a new clustering feature,
service monitoring, which allows clustering to communicate to the guest OS running
within the virtual machine and to check for service failures. If you examine the
properties of a service within Windows, actions are available if the service fails, as
shown in Figure 7. 9. Note that in the Recovery tab, Windows allows actions to be
taken on the first failure, the second failure, and then subsequent failures. These
actions are as follows:
Take No Action
Restart The Service
Run A Program
Restart The Computer