Definition - What does Horizontal Scaling mean?
Horizontal scaling is a term used in many different kinds of IT setups. The basic meaning of horizontal scaling is that systems are "built out" using additional components. By contrast, the term "vertical scaling" means that extra capability and resources are added to one single component.
Techopedia explains Horizontal Scaling
One common example of both of these kinds of scalability involves a hardware server. Suppose that network demand means a server has to handle significantly more data transfers. IT managers could add processing power or memory to the single server to increase its capability, or they could link it to other servers. The former approach illustrates vertical scaling while the latter illustrates horizontal scaling.
Horizontal scaling is often an appealing principle in IT. Some experts note that horizontal scaling is often recommended in cloud computing, where managers are taught to build out systems by introducing extra hardware. One of the benefits of horizontal scaling is that IT professionals can also use these other pieces of hardware to provide redundant data storage. Redundant data storage decreases the chances that a partial system failure will bring down the entire system or compromise operations. That is just one reason why horizontal scaling is so popular in many different kinds of IT strategies. Another reason is that IT managers can create powerful systems by simply networking low-cost generic hardware components and adding them to a system as necessary.