Horizontal scalability of a system is limited by hardware resources available in the market. For instance, scaling up RAM from 8 GB to 32 or 64 GB may be cost effective, as many products may be commonly available, but increasing it further may be cost inhibitive. Similarly, scaling up CPU is also limited by system configuration available in the market. Further doubling the hardware capability doesn't result in equal performance improvements. It's typically less.
With virtualization and cloud services, the cost of buying and maintaining hardware is coming down, making vertical scaling or clustering or scaling out more is lucrative. The increased performance of communication networks has considerably reduced the latency in the communication of nodes in the cluster. Clustering has various advantages, such as:
On-demand scaling: The nodes in the cluster can be added as and when required. We can start with a dimensioned system and keep on adding nodes as...