HA Questions - Rsync and MySQL Replication - other automation?

All, Long story short, we've got a bit of a small SaaS system we've developed that we're hosting on a dedicated server, and it runs in CPanel. We only have this account running on this dedicated server. I also want to say that I'm not a developer at all. I'm a systems and network admin, but I'm super green with Linux and MySQL, php, apache, et cetera. Nonetheless, being the everything but the kitchen "sync" :D type of admin, I can thumb my way through things enough. I've been doing some testing over the last two weeks with utilizing a combination of RSync to sync the files found in /HOME/AccountName directory, and setting up MySQL in a Master-Slave configuration to sync the databases from the master to the slave. Our ultimate goal is to have an active/passive failover server, warmsite, whatever you want to call it. We're going to have primary ServerA in one datacenter with a particular hosting provider, and ServerB (failover) in a physically disparate datacenter, with a completely different hosting provider to mitigate one particular issue causing issues with our SaaS availability. What I don't know is if there is anything outside of the /HOME/Accountname directory that I need to sync from ServerA, to ServerB to automate failover as much as possible. For example, the developer has developed this in such a way that each client gets their own dedicated database for the SaaS. I don't know if that's for better or worse, but will we have to manually create the same DB on ServerB? Also, how the clients log into the SaaS right now is via visiting . The developer has to create a subdomain in the CPanel account on ServerA in order for this to work. Would he have to also do this manually on ServerB? Last question, from what I researched "Asynchronous" replication is what's best for MySQL replication over a WAN due to latency. Is Master-Slave replication already asynchronous? We're not anywhere in need of having any kind of geographically dispersed Master-Master or Master-Master + replication quite yet, and are probably years away from that. thanks to everyone for chiming in with any answers or suggestions!