Active / active cluster
An active / active cluster is a computer network in which several computers (also called cluster nodes or the cluster nodes designated) at the same time are active. In active / active clusters, a distinction is made between the architectures Shared Nothing and Shared All .
In addition to the distribution of computing power, computer clusters are also a. used to ensure the availability of various resources such as networks, applications, etc.
In this context, an active / active configuration means that the resource secured in this way, for example a database, is active on all cluster nodes. If one node fails, the other nodes take over the processes of the failed node, there is practically no downtime, but there may be severe losses in performance because fewer systems now have to take on the same load.
The clear advantage of this concept is that the resources do not have to be redundant and the failure of a node only has performance-dependent effects on the availability of the cluster system as a whole.
The main disadvantage of such a setup is that, unlike with an active / passive configuration, the resource either directly supports an active / active configuration or has to be adapted to such a configuration, sometimes with great effort. With an active / passive configuration, on the other hand, almost any resources can be made available.
There is also the option of "hot standby" in active / passive clusters . This means that the cluster resource is active on all nodes and that it can be taken over immediately after the failure of the primary node without the process having to be started first (lengthy) on the secondary system. The failover time can be minimized in this way. However, since the secondary system is still designed redundantly and no load distribution or the like takes place, this method is not a real active / active clustering.