Here comes a new commercial storage engine for MySQL called "ScaleDB".
The architecture ScaleDB just similar like "Oracle RAC",
but now, ScaleDB only support Linux and Windows.
All the db instant are active and supports shared storage.
Expecting the storage engine be mature.
PS. If you don't have shared storage, and you just use VirtualBox as I do,
you can use "DRBD" to simulate the shared storage,
but now, DRDB only supoort Linux.
The architecture of SacleDB as below. (All pictures rights belows to www.scaledb.com)
The DRDB architecture as below. (All picture rights below to DRDB.org)
Wish this helps.