Heartbeats behave differently within a site and between sites instead of being
based on IP subnets (which still exist and are explored later in this chapter). The
cluster has two additional properties in Windows Server 2016 to support the new
site awareness: CrossSiteDelay and CrossSiteThreshold. These properties define
the time between heartbeats in milliseconds (1,000 by default) and the number of
missed heartbeats before the connection is considered down (20 by default),
respectively. These can be modified by using the following:
(Get-Cluster).CrossSiteDelay = <value>
(Get‐Cluster).CrossSiteThreshold = <value>There are two modes for site awareness: automatic and manual. To enable automatic
site-awareness based on Active Directory sites for the cluster, use this:
(Get-Cluster).AutoAssignNodeSite = 1
To manually define, you must first create the sites and then assign the site to nodes.
For example:
#Create Sites
New-ClusterFaultDomain –Name Dallas –Type Site –Description "Primary" –
Location "Dallas DC"
New-ClusterFaultDomain –Name Houston –Type Site –Description "Secondary" –
Location "Houston DC"
#Set site membership for nodes
Set-ClusterFaultDomain –Name Node1 –Parent Dallas
Set-ClusterFaultDomain –Name Node2 –Parent Dallas
Set-ClusterFaultDomain –Name Node3 –Parent Houston
Set-ClusterFaultDomain –Name Node4 –Parent Houston
Once you set the preferred site for a 2016 cluster that has sites defined, use this:
(Get-Cluster).PreferredSite = <site name, e.g. Dallas>
If you have the situation with multiactive datacenters, you can define different
preferred sites for different cluster groups that will be used to govern where VMs start
initially:
(Get-ClusterGroup
Note that because of the various levels of preference, it may be confusing which one
wins. The order of priority for placement is as follows:
1 . Storage affinity
2 . Group preferred site
3 . Cluster preferred site