Scalability is a major benefit of cloud server architecture. However, not all scaling is performed in the same way and there are some significant differences between the different scaling mechanisms.
Vertical Scaling consists of bolstering the computing power of a single server, by increasing the number of CPU cores, main memory and disk storage. However, even in the case of a virtual server, these hardware resources are not limitless. Additionally, the server may reach a point where increasing the power of one or more components does not increase its overall output.
Horizontal scaling is the placement of several similar machines in parallel.
Diagonal scaling is the combination of vertical and horizontal server scaling, which constitutes upgrading and adding components to a single server up to the critical point of cost-effectiveness, or having reached full server specification, and then replicating the server in its current configuration. This offers the most effective scaling mechanism, both in terms of price and performance.