Over the next 2-3 years we will be scaling up data collection for a project. As a result the amount of data will grow 10-fold. Our current MySQL installation can keep up with the 2Tb of data but for larger queries there is a fair amount of IOWait.

Im investigating a migration to a clustered solution to spread out the IO but am wondering about NDB and what happens to data that doesn't get accessed very often. The impression I get from reading about MySQL cluster is that it relies on memory tables for most of the data. What happens with tables that don't get accessed very often (or at all)? And how does backup work? Can I use MYSQLDUMP or is there a better solution?