And also this:
"NDB is an in-memory storage engine"
No longer true: As of MySQL 5.1.6 it's possible to store
tables on disk rather than in memory.
See http://dev.mysql.com/doc/refman/5.1/en/mysql-cluster-disk-data.html
But, I wouldn't recommend using MySQL cluster to power your
high traffic website. I've tested it but the throughput is at least 10 -
100x
worse in compare to a good old MySQL master / slave setup on the
same hardware. Esspecially the writes are slow.
SQL Relay offers load balancing functionality, without having to change
your existing code: http://sqlrelay.sourceforge.net/
Len