[From O'Reilly OSDir.com
Hold on before you decide to implement MySQL cluster, as it certainly doesn't suit all jobs yet. The MySQL NDB engine currently runs its database completely in memory. This means that you have to be able to fit your database in memory. If you have a 1GB dataset and you want to have your data spread over two nodes, you need 1GB of memory per node. If you have four nodes, you can deal with 512MB per node. The first thing that becomes clear is that you have to look at your dataset. Giant data-warehousing databases won't fit into the MySQL NDB engine yet. Today, you might need to look at commercial alternatives such as Continuent, the former Emic Networks.
Secondly, this article is about building a truly available MySQL cluster, which means it focuses on high availability, not on high throughput.
The article continues at