Scaling horizontally takes place through an increase in the number of resources (e.g.,
adding more hard drives to a storage array or adding more servers to support an application)
Scaling vertically takes place through an increase in the specifications of an individual
resource (e.g., upgrading a server with a larger hard drive or a faster CPU). On Amazon EC2,
this can easily be achieved by stopping an instance and resizing it to an instance type that
has more RAM, CPU, IO, or networking capabilities