Scaling

Scaling in system design is the process of adding increased volumes of connections data while maintaining the same system contact of reliability or availabilty.

Scaling is broken into 2 categories: Horizontal and Vertical scaling

Vertical scaling is generally the easier to understand approach which involves just adding more ram, cpu’s, disk space, or faster hardware to a single machine. Unfortunately for this approach, vertically scaling has limitations on how much hardware can be added and upgraded to a single server. Additionally costs increase much more significantly compared to the other approach which is horizontal scaling.

Advantages of vertical scaling are:

1. 1. Hardware is know and centrally located
2. 2. Upgrading is straightforward since hardware simply needs to be replaced
3. 3. Simpler to manage the system since its a single point
4. 4. Single point of deployment. No complex deployment system needs to be tweaked or changed as software changes

Disadvantages of vertical scaling are:

1. 1. Single point of failure
2. 2. Poor cost scaling
3. 3. Generally specialized skill set to work on higher end system
4. 4. Central geolocation - network latency will be an issue cross globe
5. 5. Max system load constraints

Horizontal scaling is the opposite of vertical scaling. Instead of upgrading a single machine more machines are bought. This provides its own sets of challenges, but ultimately allows more availability, performance, and cheaper hardware

Advantages of horizontal scaling are:

1. 1. Generally a lot cheaper as more hardware is added
2. 2. Lower fault tolerance
3. 3. Lower downtime
4. 4. Lessened load across the whole system

Disadvantages of horizontal scaling are:

1. 1. Increase complexity of the whole system
2. 2. Deploy process and scaling process for whole system is generally much more complex
3. 3. User and System sessions should generally be stateless for the individual servers
4. 4. Load balancers are required to distribute the load equal across the system
5. 5. Consistency is much hard since data is distributed across physical distance
6. One server may not necessarily equal one functionality