16.7.2. Assumptions and General Requirements
A replication channel requires two MySQL servers acting as
replication servers (one each for the master and slave). For
example, this means that in the case of a replication setup with
two replication channels (to provide an extra channel for
redundancy), there will be a total of four replication nodes,
two per cluster.
Each MySQL server used for replication in either cluster must be
uniquely identified among all the MySQL replication servers
participating in either cluster (you cannot have replication
servers on both the master and slave clusters sharing the same
ID). This can be done by starting each SQL node using the
--server-id=id
option, where id is a unique integer.
Although it is not strictly necessary, we will assume for
purposes of this discussion that all MySQL installations are the
same version.
In any event, servers involved in replication must be compatible
with one another with respect to both the version of the
replication protocol used and the SQL feature sets which they
support; the simplest and easiest way to assure that this is the
case is to use the same MySQL version for all servers involved.
Note that in many cases it is not possible to replicate to a
slave running a version of MySQL with a lower version number
than that of the master — see
Section 6.6, “Replication Compatibility Between MySQL Versions”, for details.
We assume that the slave server or cluster is dedicated to
replication of the master, and that no other data is being
stored on it.
