Examples: Resource group behavior in clusters that have sites

The fallback policy applies to the ONLINE and ONLINE SECONDARY instances of the resource group.

Note: Sites are supported only in PowerHA® SystemMirror® 7.1.2, or later, in both the Enterprise Edition and the Standard Edition. Replication management is supported only in PowerHA SystemMirror Enterprise Edition.

The intersite management policy for a resource group determines the fallback behavior of the ONLINE instances of the resource groups between sites, which governs the location of the secondary instance.

The ONLINE SECONDARY instance is located at the site that does not have the ONLINE instance. The following table shows the expected behavior of resource groups during site events according to the startup and intersite management policies.

Note: Most of the restrictions in the following table apply only when multiple interfaces per node are on the same network. When only one interface per node is on the network, which can be common when using ether the Fibre Channel or virtual Ethernet, most of these restrictions do not apply.


Nodestartup policy (applies within site)	Intersite management policy	Startup, fallover, or fallback behavior
Online on home node only	Prefer primary site	Cluster Startup Primary site The home node acquires the resource group in the ONLINE state. Nonhome nodes leave the resource group. Secondary site The first node that joins this site acquires the resource group in ONLINE SECONDARY state. Intersite fallover The ONLINE instance falls between sites when no nodes at the local site can acquire the resource group. The secondary instance moves to the other site and is brought to the ONLINE SECONDARY state on the highest priority node that is available, if possible. Intersite fallback The ONLINE instance falls back to the primary site when a node from the primary site joins. The secondary instance moves to the other site and is brought to the ONLINE SECONDARY state on the highest priority node that is available, if possible.
Online on first available node or Online using node distribution policy	Prefer primary site	Cluster Startup Primary site The node that joins first from the primary site, and meets the criteria, acquires the resource group in the ONLINE state. The resource group is OFFLINE on all other nodes at the primary site. The node distribution policy applies only to the primary instance of the resource group. Secondary site The first node to join the cluster in this site acquires all secondary instances of resource groups with this startup policy in the ONLINE_SECONDARY state (no distribution). Intersite fallover The ONLINE instance falls between sites when no nodes at the local site can acquire the resource group. The secondary instance moves to the other site and is brought to the ONLINE SECONDARY state on the highest priority node that is available, if possible. Intersite fallback The ONLINE instance falls back to the primary site when a node from the primary site joins. The secondary instance moves to the other site and is brought to the ONLINE SECONDARY state on the highest priority node that is available, if possible.
Online on all available nodes	Prefer primary site	Cluster Startup Primary site All nodes acquire the resource group in the ONLINE state. Secondary site All nodes acquire the resource group in the ONLINE_SECONDARY state. Intersite fallover The ONLINE instances fall between sites when all nodes at the local site go OFFLINE or fail to start the resource group. The secondary instances move to the other site and are brought to the ONLINE SECONDARY state where possible. Intersite fallback ONLINE instances fall back to the primary site when a node on the primary site rejoins. Nodes at the secondary site acquire the resource group in the ONLINE_SECONDARY state.
Online on home node only	Online on either site	Cluster Startup Primary site The home node that joins the cluster (from either site) acquires the resource group in the ONLINE state. Nonhome nodes leave the resource group OFFLINE. Secondary site The first node to join from the other site acquires the resource group in the ONLINE_SECONDARY state. Intersite fallover The ONLINE instance falls between sites when no nodes at the local site can acquire the resource group. The secondary instance moves to the other site and is brought to the ONLINE_SECONDARY state on the highest priority node available, if possible. Intersite fallback The ONLINE instance does not fall back to the primary site when a node on the primary site rejoins. The highest priority rejoining node acquires the resource group in the ONLINE_SECONDARY state.
Online on first available node or Online using node distribution policy	Online on either site	Cluster Startup Primary site The node that joins first from either site, that meets the distribution criteria, acquires the resource group in the ONLINE state. Secondary site After the resource group is ONLINE, the first joining node from the other site acquires the resource group in the ONLINE_SECONDARY state. Intersite fallover The ONLINE instance falls between sites when no nodes at the local site can acquire the resource group. Intersite fallback The ONLINE instance does not fall back to the primary site when the primary site joins. A rejoining node acquires the resource group in the ONLINE_SECONDARY state.
Online on all available nodes	Online on either site	Cluster Startup Primary site The node that joins first from either site acquires the resource group in the ONLINE state. After an instance of the group is active, the remaining nodes in the same site also activate the group in the ONLINE state. Secondary site All nodes acquire the resource group in the ONLINE_SECONDARY state. Intersite fallover The ONLINE instance falls between sites when all nodes at the local site go OFFLINE or fail to start the resource group. Intersite fallback The ONLINE instance does not fall back to the primary site when the primary site joins. Rejoining nodes acquire the resource group in the ONLINE_SECONDARY state.
Online on all available nodes	Online at both sites	Cluster Startup All nodes at both sites activate the resource group in the ONLINE state. Intersite fallover No fallover occurs. Resource group is either in the OFFLINE state or in the ERROR state. Intersite fallback No fallback occurs.