PostgreSQL Replication/Clustering solution

Hi you all.
I'm asked to do a report about Replication/Clustering for PostgreSQL. I need
to report about what kind of tools does exist and compare them, and finally
propose a solution to implement in the company's database.
I have a poor idea about replication/clustering issues (and about writing
english, you can see it), so I'd be glad to be helped by you.
Here is a brief description of our model:
There are a lot of "component servers" (CS) that provide the frontend
services. These CS hosted in diferent servers work with databases hosted in
the unique main "database server".
We are adding periodically more CS because the growing number of users.
Adding these CS solves succesfully the scalability problem in this point of
view, but the database is becoming over-required due this situation.
So, I need to look for solution on database to solve the following problems:
- scalability as the 1st priority.
- reliability as the second priority (system failure, disaster avoiding,
etc).
- performance as a future problem to solve (phisically distributed CS with
local/remote access).
So, which kind of solution, orientated on Replication/Clustering, are
available for ProspectSql? And which are the "pros and cons" for each one
for our priorities to solve?

Thanks, and sorry for my english.

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