Question

What’s the difference between peer-to-peer replication and merge replication using SQL Server?

Answer 1

1. Peer-to-Peer Transactional
   Replication is typically used to support
   applications that distribute read
   operations across a number of server
   nodes.

Although peer-to-peer replication enables scaling out of read operations, write performance for the topology is like that for a
single node, this is because ultimately all inserts, updates, and
deletes are propagated to all nodes. If one of the nodes in the system
fails, an application layer can redirect the writes for that node to
another node, this is not a requirement but does maintain availability if a node fails.

See: Peer-To-Peer Replicaiton

2. Merge Replication is bi-directional
   i.e. read and wrtie operations are
   propogated to and from all nodes.
   Merge replication often requires the
   implementation of conflict
   resolution.

See: How Merge Replication
Works