The SafeKit software provides a simple active active cluster with real-time replication on Windows or Linux. Applications are running on two servers in mutual failover. Each server is backup of the other server. And each application works on its own replicated file directories.
If one server fails in an active active cluster, all applications will be active on the same server. After restart of the failed server, applications will return to run on their default primary server.
The SafeKit active active cluster is simply configured by deploying two mirror modules with real-time replication. Each mirror module contains its own configuration of virtual IP address, real-time replicated directories and restart scripts.
The Hyper-V replication automatic failover and load balancing solution is an example of an active-active cluster with N mirror modules replicating N virtual machines between two physical servers. In this configuration, a mirror module replicates a full virtual machine and restarts the virtual machine in case of failure. There is no virtual IP in such a module because restarting a VM on a server makes automatically the IP failover of the VM. And an application is installed in one single VM in this architecture.
As presented in the Hyper-V cluster demonstration, an active active cluster can implement real-time data replication for directories inside the operating system disk. Note that replicating data inside the system disk is possible with byte-level file replication and impossible with block-level disk replication.
Another way to implement an active active cluster with SafeKit is the network load balancing cluster described here.
Here are some examples of mirror application modules:
Here are some examples of farm application modules: