Abel Perez in a post about Cassandra:
Horizontal scalability boils down to the ability to add new hardware to a system without any interruption or downtime. An ideal horizontally scalable system does not require reconfiguration and supports incremental addition of hardware.
Nope. This is the definition of elasticity.
Horizontal scalability is the capability of a system to accept adding or removing multiple nodes (independent units of resources) and making them work as a single system. The scalability of a system can be further categorized as: negative, sub-linear, linear, or supra-linear depending on the shape of the performace1/nodes curve
This is the part where things can get more complicated as there are multiple ways to characterize the performance of a system (e.g. throughput, latency, etc.) ↩
Original title and link: Horizontal Scalability vs Elasticity ( ©myNoSQL)