MDB Questions - switching to MDB, failover and so on...

Hi, We've relied on PEAR::DB and DB_DataObject for quite some time now. But the more I read about MDB the more attractive it looks, but I have a couple questions. How hard is it to move from DB to MDB, especially in the context that we need to continue to use DB_DataObject? Are the APIs compatible? What steps might need to be taken? Do any of the db layers support automated failover? We were trying to do this because we are going to be implementing replication but we found things a bit inflexible using just DB so we're probably going to rely on hardware failover instead. Has anyone considered this as a feature to add on the/a software layer? Many thanks, -- -- Matt