Note: Supported from NetScaler 10.5 Build 52.1115.e onwards.
Nodegroups can be configured such that when one nodegroup goes down, another nodegroup can take over and process traffic. For example, when a nodegroup NG1 goes down, NG2 takes over.
Note: This functionality can be used to configure datacenter redundancy where each nodegroup is configured as a datacenter.
To achieve this use case, cluster nodes must be logically grouped into nodegroups, where some nodegroups must be configured as ACTIVE and others as SPARE. The active nodegroup with the highest priority (that is, the lowest priority number) is made operationally active and therefore serves traffic. When a node from this operationally active nodegroup goes down, the node count of this nodegroup is compared with the node count of the other active nodegroups in order of their priority. If a nodegroup has a higher or equal node count, that nodegroup is made operationally active. Else, the spare nodegroups are checked.
The following figure shows a nodegroup setup that has nodegroup redundancy defined. NG1 is initially the active nodegroup. When it loses one of the nodes, the spare nodegroup (NG3) with the highest priority starts serving traffic.
Configuring redundancy for nodegroups