Traditionally, Scale up methods are used to increase the power of an enterprise server. Here, concurrent programming methodology is leveraged using multi-core architecture in the context of a single application in an enterprise world.
In the modern world, Scale out design is followed to implement the scalability of any enterprise infrastructure. Highly distributed programming is the foundation for this model, which works by distributing the given job across the connected machines throughout the network:
Legacy mainframe and modern Hadoop processing are the best suitable examples for the Scale up and Scale out designs respectively. It will be easy to understand the fundamental design change with the right example.
During mainframe days, the vertical scaling/scale up was used to upgrade the capacity of the existing server by adding more processors and memory. This process was not only costlier, but also could not scale beyond a threshold. On the other hand, horizontal scaling/scale out refers to adding more servers with less processors and memory. Usually, Scale out is not only cheaper in terms of the overall cost, but can also, literally, scale infinitely without any limitation.
To make the comparison clear, the following table lists the differences between Scale up and Scale out, based on the fundamental design concepts and implementation specifications of an enterprise application:
| S.No. | Design element | Scale up | Scale out |
| 1 | Fault tolerance | Great risk | Easy by design |
| 2 | Upgrade mechanism | High effort | Easy to implement |
| 3 | Elasticity (on demand) | Remote chance | Easy to build |
| 4 | TCO (Total Cost of Ownership) | Large | Medium |
| 5 | Adaptation to the modern cloud model |
Difficult | Easy |
| 6 | Utility cost (electricity and cooling charges) | Relatively less | High |
| 7 | Network equipment like switches and routers | Medium | High |
| 8 | License quantity | Moderate | High |
| 9 | Agile methodology | Challenge to follow | Easy adoption |
Based on your enterprise need, limitations, and so on, it is highly recommended to choose either Scale up or Scale out as the right fit. It should be a wise and careful decision taken by the infrastructure and enterprise architects of the firm.