I know next to nothing about having more than one server work together. Right now I've been playing around with the cloud servers offering from rackspace.
All the time when people talk about these types of "cloud" servers, they make it sound like it's so easy to scale. Now it is easy to scale vertically. But I'm talking horizontally. I know with cloud servers you can save the image of your server and spin up a new server with exactly the same image. How do you make use of having more than one server? How do you insure database integrity in you application? People make it sound so simple and like you can just add a couple here and take a couple there.
Also, with cloud servers you can scale from 256mb to around 16gb. At what point is it better to scale horizontally rather than vertically? I'd imagine there's one bottleneck would be the disk, and scaling horizontally would be better so you could have more disks. But maybe I'm wrong and you're supposed to scale vertically all the way and then horizontally?