I was just in the process of 'yum updating' a server. One of the updates its suggesting to carry out is an upgrade from mysql 5.1 to 5.5.

The mysql server operates in a master-master replication setup with another 5.1 mysql instance. I would also update the other master to 5.5, but want to keep one online at all times. This master also has a number of 5.1 mysql slaves replicating from it.

Does anyone know if:

1. yum update is safe from 5.1 to 5.5 without huge data rebuilds
2. if the above replication setup will be a problem.

Edit: This is a centos 5.4 install. However the updates are coming in from the non-standard remi repo.