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MySQL - Replication Implementation Overview
MySQL replication is based on the server keeping track of all changes to your database (updates, deletes, etc) in the binary
log. and the slave server(s) reading the saved queries from the master server's binary
log so that the slave can execute the same queries on its copy of the data.
It is very important to realize that the binary log is simply a record starting from a fixed point in time (the moment you
enable binary logging). Any slaves which you set up will need copies of all the data from your master as it existed the
moment that you enabled binary logging on the master. If you start your slaves with data that doesn't agree with what was on
the master when the binary log was started, your slaves may fail.
A future version (4.0) of MySQL will remove the need to keep a (possibly large) snapshot of data for new slaves that you
might wish to set up through the live backup functionality with no locking required. However, at this time, it is necessary
to block all writes either with a global read lock or by shutting down the master while taking a snapshot.
Once a slave is properly configured and running, it will simply connect to the master and wait for updates to process. If
the master goes away or the slave loses connectivity with your master, it will keep trying to connect every
master-connect-retry seconds until it is able to reconnect and resume listening for updates.
Each slave keeps track of where it left off. The master server has no knowledge of how many slaves there are or which ones
are up-to-date at any given time.
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