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If I were to set up cyclical replication between a MySQL 5.6 master server and a MySQL 5.1 master server, what are some things that could potentially go wrong?

Also, the 5.6 MySQL does not have GTID enabled.

Thanks IS

user1805458
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2 Answers2

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Cringe, gag, etc.

5.1 and 5.6 differ by 2 major versions. Replication is 'guaranteed' to work one direction, not the other.

Don't turn on GTIDs in 5.6; 5.1 will not like it.

Don't use any features new to 5.5 or 5.6.

Simply, don't do it. Get the 5.1 upgraded ASAP.

Rick James
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  • Agreed. Failure is very likely, in such an environment. To put a fine point on it, this setup isn't guaranteed to work in *either* direction. [*"MySQL supports replication from one major version to the next higher major version."*](https://dev.mysql.com/doc/refman/5.6/en/replication-compatibility.html). Specifically, that means *from* and older master and *to* a newer slave, only. In circular replication, both servers have both roles, and a newer master with an older slave *"may be possible, but is generally not supported"*. There are too many changes for backwards replication to be safe. – Michael - sqlbot Apr 28 '15 at 19:41
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Replication from MySQL 5.x to 5.6 has a bear trap just waiting for you.

In Michael's comment, he stated the politically accept premise : "MySQL supports replication from one major version to the next higher major version.". He also said "this setup isn't guaranteed to work in either direction."

I have a very interesting caveat on going from 5.x to 5.6: There are some rare occasions when a binlog event from a pre-5.6 master cannot be interpreted by 5.6 slave and stops replication cold. I wrote about this in January (See my post mysql replication master 5.5 slave 5.1 error on create database)

I concluded my old post with this

If this crazy scenario was possible from a MySQL 5.5.30 Master to MySQL 5.6.21 Slave, (as I have shown happen and two maintenance cycles to correct), then the reverse is far more likely (the reverse being a new Master and an older Slave).

You do not want circular replication for 5.1/5.6. While you can replicate from 5.1 to 5.6, please don't stay long in that setup. The binlog format differences are very slight, but different enough to break replication. As @RickJames said "Simply, don't do it. Get the 5.1 upgraded ASAP."

While I could expound just on circular replication, I refer you to

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RolandoMySQLDBA
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