Mysql – configure MySQL Replication as Master – Master – Slave

Using replicate-wild-do-table=% is not the correct way to get complete replication. That would seem sensible, but here's why it isn't:

• The replicate-* options are restrictive by their presence. The *-do-* options seem to be telling the server what to "do," but in fact they are telling the server what to only do.

• The complete absence of any replicate-* configuration variables means "replicate everything."

In the simplest case, when there are no --replicate-* options, the slave executes all statements that it receives from the master. Otherwise, the result depends on the particular options given. -- http://dev.mysql.com/doc/refman/5.5/en/replication-rules.html

That, I think, is the point you are needing. It holds true for all MySQL 5.x.

Once you enable binary logging, set the server-id values on each machine, synchronize the data sets, CHANGE MASTER TO ..., and then START SLAVE, then you should have a working configuration where all DML and DDL will be replicated and your servers will be identical replicas of each other.

If you started out with identical data sets, everything should behave exactly as you would expect it to.

What MySQL replication does best and simplest is replicate entire data sets among servers without any restrictions. Trying to restrict replication to a subset of the data is a process that should carry a warning label that ends with the phrase "...unless you really know what you're doing."

When you use the --replicate-* options, the document cited above also offers this tip:

it is recommended that you avoid mixing “do” and “ignore” options, or wildcard and nonwildcard options

You are using a mix of these, which adds complexity and may explain why your DDL didn't replicate as you expected it to.

The simple answer is No.

In Mysql replication, Master copies the bin log files to slaves, and after that, it's work is over. Now the Slave will run the bin files and execute them, but there won't be any performance on Master.

There might be scenario where you are using full synchronous replication, in which master will wait for the slave to execute the query, but again it won't impact the performance in terms of memory or CPU, but the master will wait for the query to be executed.

Also, for your second question, Phil already answered it, that ssh sends data through encryption which uses a lot of CPU, hence if you want other ways, use the other methods which are described by Phil.