# Upgrading major MySql version on a multi-master pair

**URL:** <https://forums.percona.com/t/upgrading-major-mysql-version-on-a-multi-master-pair/1743>\
**Category:** Other MySQL® Questions\
**Created:** [January 27, 2012, 10:50am UTC](https://forums.percona.com/t/upgrading-major-mysql-version-on-a-multi-master-pair/1743 "2012-01-27T10:50:11Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![osolo](https://avatars.discourse-cdn.com/v4/letter/o/d26b3c/32.png) [@osolo](https://forums.percona.com/u/osolo)\
**Post date:** [January 27, 2012, 10:50am UTC](https://forums.percona.com/t/upgrading-major-mysql-version-on-a-multi-master-pair/1743/1 "2012-01-27T10:50:11Z")

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We’re currently in the process of upgrading from MySql 5.0 to 5.5.

We have the edge slaves upgraded and the SQL incompatibilities debugged. All that’s left now is upgrading the production masters.

Ideally, we could pick one of the two masters, say B, and upgrade it to 5.5. We would then make it the writer for a while and test to ensure it can handle to load and there are no problems. At that point we would also upgrade A.

The snag is that, to the best of my knowledge, we can’t have B (on 5.5) replicating to A (still on 5.0) because 5.0 won’t be able to handle the 5.5 replication stream. To promote B to “writer” status, we’d have to take A offline and there would be no going back. If MySql 5.5. can’t handle the load for whatever reason, we’re screwed.

I’m hoping someone on this forum went through a similar upgrade and has a better idea!

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**Author:** ![revin](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/revin/32/824_2.png) [@revin](https://forums.percona.com/u/revin)\
**Post date:** [February 1, 2012, 6:20pm UTC](https://forums.percona.com/t/upgrading-major-mysql-version-on-a-multi-master-pair/1743/2 "2012-02-01T18:20:00Z")

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Attach one of the 5.0 slave to one of the 5.5 edge slaves and let it run for a week and see if any problem crops up. Then pt-log-player and pt-upgrade are your friends 🙂[http://www.mysqlperformanceblog.com/2011/12/29/how-to-test-y](http://www.mysqlperformanceblog.com/2011/12/29/how-to-test-y) our-upgrades-pt-upgrade/