Information Technology Reference
In-Depth Information
Network
partition
is the term used to describe the situation in which one or more slave hosts
cannot communicate with the master even though they still have network connectivity with
each other. In this case, vSphere HA is able to use the heartbeat datastores to detect whether
the partitioned hosts are still live and whether action needs to be taken to protect VMs on those
hosts or initiate an election for a new master within the network partition.
Network
isolation
is the situation in which one or more slave hosts have lost all management
network connectivity. Isolated hosts can neither communicate with the vSphere HA master
nor communicate with other ESXi hosts. In this case, the slave host uses heartbeat datastores to
notify the master that it is isolated. The slave host uses a special binary i le, the host-
X
-
poweron i le, to notify the master. The vSphere HA master can then take the appropriate
action to ensure that the VMs are protected. We'll discuss network isolation and how an ESXi
host reacts to network isolation later in this chapter in the section “vSphere High Availability
Isolation Response.”
Figure 7.14 shows the i les on a VMFS datastore that vSphere HA uses for storage heartbeat-
ing between the vSphere HA master and slave hosts.
Figure 7.14
vSphere HA uses
the host-
X
-
poweron fi les for a
slave host to notify
the master that it
has become isolated
from the network.
In the section “Setting vSphere High Availability Datastore Heartbeating,” we'll show you
how to see which datastores are used as heartbeat datastores as well as how to tell vSphere HA
which datastores should or should not be used for heartbeating.
With this overview of the vSphere HA architecture and behavior under your belt, let's move
on to enabling vSphere HA to protect your VMs.
Enabling vSphere High Availability
To implement vSphere HA, all of the following requirements should be met:
All hosts in a vSphere HA-enabled cluster must have access to the same shared storage
locations used by all VMs on the cluster. This includes any Fibre Channel, FCoE, iSCSI, and
NFS datastores used by VMs.
◆
All hosts in a vSphere HA cluster should have an identical virtual networking coni gura-
tion. If a new switch is added to one host, the same new switch should be added to all hosts
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