One thing that we announced in the GA release of MySQL Cluster 8.0 is
that we now support using 3 and 4 replicas. Actually the NDB software
was designed to support 1 through 4 replicas from the very get go in the
1990s. The reason it has not been supported is simply that we haven't
had any regular testing effort attached to it. Thus we haven't felt that
we can support such an important feature without having proper testing
of it.

What we did in the development of MySQL Cluster 8.0 is that we have
added a number of new configurations with both 3 replicas and with
4 replicas. These configurations will now be used in our daily testing
of NDB.

In the process of working on this we found some issues with arbitration
already in MySQL Cluster 7.6. This issue was fixed in 7.6 already.
So the way to decide how to handle a node failure in 7.6 and …

This post is an extension to my earlier posts about multi master replication cluster multi master replication in mysql and mysql multi master replication act II The problem I had encountered and discussed was with automatic failover. What happens when the master goes down? How can either a slave or another master be promoted to become the master? Once the settings are done on all the mysql dbs

I have worked as an architect in the MySQL/NDB world for more than 20 years and I am still working at Oracle and I like it here. Given all the FUD spread about MySQL I thought it might be a good idea to spread the word about all the great things we're doing to MySQL at Oracle.

#1 We are working on improving modularity in MySQL code base
In the early days of MySQL the MySQL development had serious issues with its development model. It was a model designed for a small code base. I used to work at Ericsson which is developing telecom switches that have systems with tens of millions lines of code. Such large systems require modularity. The Ericsson switches was developed with modularity built into the programming language already since the 70's. Even with this modularity a second level of modularity was required. The learnings from this reengineering project that span over more than a decade has given me valuable insights …

Lets see what HA solutions can be designed in mysql and where are they suited.

1. Single master - single slave.

M(RW)|S(R) A simple master slave solution can be used for a small site - where all the inserts go into the master and some (non-critical) requests are served from the slave. In case if the master crashes, the slave can be simply promoted as the master - once it has replicated the "