One good way to pull off something of that nature is to set up Master-Master Replication or Circular Replication. This is not to be confused with MultiMaster Replciation.
Setting up Circular Replication is actaully very easy if you have setup Master-Slave Replication. Here is what you need to do in order to configure it.
For this example, we will assume Master-Slave Replication is active but you will experience a bit of downtime (1-2 minutes):
Step 1) Add this line to /etc/my.cnf on the Master.
log-slave-updates
Step 2) Add these line to /etc/my.cnf on the Slave:
log-bin=mysql-bin (or have whatever the master has for this)
log-slave-updates
WARNING : Here is the brief moment of downtime !!!
Step 3) On the Slave, service mysql restart
This will activate binary logs on the Slave
Step 4) On the Master, service mysql stop
Step 5) Use rsync to copy the /var/lib/mysql folder of the Slave to the Master.
WARNING : Here is the longer moment of downtime !!!
Step 6) On the Slave, service mysql stop
Step 7) On the Slave, find out the last binary log
Step 8) On the Slave, find out the filesize of the last binary log
Step 9) Use rsync to copy the /var/lib/mysql folder of the Slave to the Master. This should be a faster copy.
Step 10) On the Master, edit
Line 2 of master.info with the last binary log of the Slave.
Line 3 of master.info with the filesize of the last binary log of the Slave.
Line 4 of master.info with the IP of the Slave.
Line 5 is the userid of replication user (DO NOT TOUCH)
Line 6 is the password of replication user (DO NOT TOUCH)
Step 11) Delete all binary logs and binary log index file of the Master.
Step 12) On the Slave, service mysql start, wait 15 seconds
Step 13) On the Master, service mysql start
Step 14) On the Master, run STOP SLAVE; SHOW MASTER STATUS;
Step 15) On the Slave, run CHANGE MASTER TO MASTER_HOST='IP of Slave',MASTER_USER='userid of replication user from Step10',MASTER_PASSWORD='password of replication user from Step10',MASTER_LOG_FILE='binary log from Step14',MASTER_LOG_POS=LogPos from Step14.
Step 16) On the Slave, run START SLAVE;
Step 17) On the Master, run START SLAVE;
I performed steps similar to this for another StackExchange question I answered.
Give it a Try !!!
Best Answer
You can use any of the available ETL Tools:
Initial size not important, the most important is the daily number of changes.
You will need to add a timestamp for
INSERT/UPDATEor a bit column and triggers to mark the new sync status.My clients sync millions-row databases (DB2/MySQL/Web) by
cronjobs.An other solution may be SymmetricDS (read the article about transformation of data using it: http://www.symmetricds.org/doc/3.0/html-single/user-guide.html#transform-data).