Hotha,
are you expecting to run / to login to the second, replicated Alfresco system? If not you make sure to replicate your alf_data/contentstore server directory (rsync jobs, block based replication, ...) and to set up a db replication. You should not start the second Alfresco system if you don't know what you're doing since you may corrupt your repository db.
If you intend to use both Alfresco installations on the same time (even in "read-only" mode) you need something like Alfresco cluster technology which is not part of the Community Edition (but there is a commerical cluster offer for the CE and a specific geo repo replication solution for EE).
Alfresco Replication is not a real replication but a copy job which creates a new independant node in the second system. The copied node has no metadata and a different node id). Alfresco Replication is not designed as a desaster recovery solution. We implemented a more sophisticated solution which is a more or less one way async Server2Server sync wich also replicates defined metadata but this is maybe also not what you expect?
If you expect to run more than one Alfresco system in an active mode clustering is not the perfect solution because it will slow your whole system down dramatically if not running in a low latency network. Instead you would need an async services which supports a locking mechanism respected from all involved systems to avoid conflicts which are very hard to handle. Unfortunately there is no such solution available I know of but maybe some will correct me?
Hotha,
could you please describe the solution and requirements more in detail, what your customer / your users expect?
