Question

what is horizontal scaling and vertical scaling

Answer 1

The heart of the difference is the approach to adding computing resources to your infrastructure. Withvertical scaling (a.k.a. “scaling up”), you’re adding more power to your existing machine. In horizontal scaling (a.k.a. “scaling out”), you get the additional resources into your system by adding more machines to your network, sharing the processing and memory workload across multiple devices.

One way to look at it is to think of vertical scaling like retiring your Toyota and buying a Ferrari when you need more horsepower. With your super-fast car, you can fly at top speed with the windows down and look amazing. But, while Ferraris are awesome, they’re not very practical, they’re expensive, and at the end of the day, they can only take you so far before they’re out of gas. (Not to mention, there’s only two seats!)

Horizontal scaling gets you that added horsepower – not by ditching the Toyota for the Ferrari, but by adding another vehicle to the mix. In fact, you can think of horizontal scaling like several vehicles you can drive all at once. Maybe none of these machines is a Ferrari, but no one of them needs to be: across the fleet, you have all the horsepower you need.

Why Scaling Out Is Better Than Up

When you’re choosing between horizontal scaling and vertical scaling, you also have to consider what’s at stake when you scale up versus scale out.

In the Toyota-for-Ferrari trade-in scenario, you’re replacing a slower server with a bigger, faster one.

When you do this, though, you’re throttling yourself while the machine is taken offline for the upgrade. And, what happens down the road when your traffic is on the rise again and you have to repeat the upgrades? There are only a finite number of times you can go about solving your problem by “scaling up” in this manner.

Horizontal scaling is almost always more desirable than vertical scaling because you don’t get caught in a resource deficit. Instead of taking your server offline while you’re scaling up to a better one, horizontal scaling lets you keep your existing pool of computing resources online while adding more to what you already have. When your app is scaled horizontally, you have the benefit of elasticity.