Postgres-R is an extension to the relational database system Postgres providing efficient, fast and consistent database replication.
Learn more about Postgres-R
There are many approaches available to scale PostgreSQL beyond running on a single server. An outline of the terminology and basic technologies involved is at High Availability and Load Balancing. There is a presentation covering some of these solutions.
There is no one-size fits all replication software. You have to understand your requirements and how various approaches fit into that. For example, here are two extremes in the replication problem space:
You have a few servers connected to a local network you want to always keep current for failover and load-balancing purposes. Here you would be considering solutions that are synchronous, eager, and therefore conflict-free.
Your users take a local copy of the database with them on laptops when they leave the office, make changes while they are away, and need to merge those with the main database when they return. Here you'd want an asynchronous, lazy replication approach, and will be forced to consider how to handle conflicts in cases where the same record has been modified both on the master server and on a local copy.
These are both database replication problems, but the best way to solve them is very different. And as you can see from these examples, replication has a lot of specific terminology that you'll have to understand to figure out what class of solution makes sense for your requirements. A great source for this background is in the PostgreS-R Terms and Definitions for Database Replication. The main theoretical topic it doesn't mention is how to resolve conflict resolution in lazy replication cases like the laptop situation, which involves voting and similar schemes.
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