The aim is to share the load of accessing data, hence many "read" databases. For now I plan to go with gmax's suggestion of having an application wrapper.
Ok. If it was mainly redundency I was going to suggest you look at DRBD but it's *not* going to help your performance!
DRBD is a block device which is designed to build high availability clusters. This is done by mirroring a whole block device via (a dedicated) network. You could see it as a network raid-1.