Information Technology Reference
In-Depth Information
Does vCenter Server Talk to vSphere HA Slave Hosts?
h ere are a few instances in which vCenter Server will talk to vSphere HA agents on slave hosts:
W hen it is scanning for a vSphere H A master, when a host is reported as isolated or partitioned, or
if the existing master informs vCenter that it cannot reach a slave agent.
Once an ESXi host in a vSphere HA-enabled cluster elects a vSphere HA master, all
other hosts become slaves connected to that master. The slave hosts have the following
responsibilities:
A slave host watches the runtime state of the VMs running locally on that host. Signii cant
changes in the runtime state of these VMs are forwarded to the vSphere HA master.
◆
vSphere HA slaves monitor the health of the master. If the master fails, slaves will partici-
pate in a new master election.
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vSphere HA slave hosts implement vSphere HA features that don't require central coordi-
nation by the master. This includes VM health monitoring.
◆
The role of any given ESXi host within a vSphere HA-enabled cluster is noted on the
Summary tab of the ESXi host within the vSphere Web Client. The composite screenshot in
Figure 7.13 shows how the vSphere Web Client presents this information.
Figure 7.13
h e status of an
ESXi host as either
master or slave is
provided on the
host's Summary
tab. Here you can
see both a master
host and a
slave host.
We mentioned that vSphere HA uses the management network as well as storage devices to
communicate. In the event that the master cannot communicate with a slave across the manage-
ment network, the master can check its
heartbeat
datastores
—selected datastores used by vSphere
HA for communication—to see if the slave host is still alive. This functionality is what helps
vSphere HA deal with network partition as well as network isolation.
