----- Original Message ----- From: <[EMAIL PROTECTED]>
To: "Chris Knipe" <[EMAIL PROTECTED]>
Cc: <mysql@lists.mysql.com>
Sent: Monday, February 28, 2005 7:11 PM
Subject: Re: two-way replication
"Chris Knipe" <[EMAIL PROTECTED]> wrote on 02/28/2005 11:53:14 AM:
Hi,
Is two-way replication possible with MySQL 5.x? Any good sites / docs describing this type of setup?
-- Chris.
By "two-way" replication, do you mean "changes to either database are synchronized to the other"? This is a dual-master situation and not yet supported by MySQL. The problem is with cross-server locking. Right now (even with v5.0) MySQL does not know to lock a record on your "other" server to prevent someone over "there" from changing that record while you are editing it on "this" server. Same goes for inserts (auto_increment values are not coordinated) and deletes.
Now, I have been monitoring the development lists on the MySQL Cluster and MySQL Federated lines and both are working on inter-server coordination but I have no idea if either of those products will fit your need.
As of today, MySQL does support 1-way, and chained replication. There is no rule that prevents you from creating circular replication by making each server the "child" of the other. The danger with circular replication is that you need to ensure (by application-level logic, data partitioning, or any of other techniques) that insert collisions do not occur (no two new records get the same primary key from different servers) and that you can gracefully handle simultaneous updates (as they are not prevented at the server level).
Search this list's and the other lists' archives (http://lists.mysql.com/) for some pretty clever workarounds to help stabilize circular replication. During your searches, you will find links to several books that are online, I highly recommend you read ALL of those links.
Thanks Shawn,
I will look into it as well as clustering. I think clustering may solve my problems, I am not sure myself to be honest.
We basically operate a large WAN, and due to time critical queries on the databases (such as Radius AAA), I want to find a way to roll out multiple databases at strategic locations on the network. The problem comes in that all these databases MUST handle INSERT, SELECT, UPDATE, and DELETE propperly, and migrate any changes through all the databases servers on the network (for now, it will just be 2, but I'm sure this will become more soon).
I have to admit, I haven't been following the MySQL developments too much since 4.x came out, so yes, I do have some reading to do.
Thanks again for your input.
-- Chris.
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