I posted this a version of this on my blog but haven't gotten nearly the responses I had hoped. Hoping someone here can help me instead.

I’ve been trying to figure out if a MySQL Cluster would make sense in our environment and if it’s worth the complexity. I think so but I can’t find enough information online to answer some nagging questions.

Mozilla has several "pairs" of servers (master/slave, sometimes slaves). It's a balancing act to move databases around when a pair gets hammered which usually involves some sort of downtime but less so then when we determine we need to add another slave.

What I want is to be able to throw more machines into a cluster to increase I/O, CPU or number of client connections & queries I can handle without a lot of effort. On paper, MySQL Cluster looks like it’ll do that but I’m left with a bunch of questions:

1. What do I do if disk I/O is my contention? CPU? 2. If I need more capacity on my read-write heads, do I just add more SQL nodes? Do my apps just need to know of multiple heads? 3. How are simultaneous database writes (updates/inserts) handled? Will I run into locking issues? 4. How critical is the management node? If it stops running, what breaks?

I’m hoping someone out there’s been through these issues and can point me in the right directions.