Scale Up and Scale Out

Reference: library.gabia.com

Two Methods for Server Expansion - Scale Up, Scale Out

When more server capacity and performance are needed, you can expand the system using two methods: Scale Up and Scale Out

1. Scale Up

• Scale-up means increasing the server's own performance by adding CPU or RAM to the server, or replacing it with higher-performance components or a server

  • In other words, it means upgrading from the existing server to a higher-performance server

    • Also called "Vertical Scaling"

• Since all data is processed on a single server, it is a suitable method for DB Servers where data updates occur frequently


Problems with Scale-up

• Since all the load is concentrated on a single server, there is a risk of being significantly affected in the event of a failure

• The problem of scalability limitations of the storage controller

• Migration costs that arise when performance & capacity expansion limits are reached and a new system needs to be added

2. Scale Out

• A method of improving processing capability by increasing the number of servers with the same or similar specifications as the existing server

  • Also called "Horizontal Scaling"

• Expansion is somewhat more flexible compared to Scale-up

• Since there are multiple servers, load balancing must be implemented to evenly distribute the load across each server


Advantages of Scale Out

• Even if one server goes down due to a failure, service can continue to be provided through other servers

Problems with Scale Out

• Since all servers must have the same data, it is a suitable method for web servers where data changes are infrequent

• Difficulty in designing and implementing Parallel Computing

  • There are fundamentally parts that need to be serialized (single processing),

  • There are bandwidth and synchronization issues, and

  • Performance does not simply increase as cores increase; bandwidth increases with the number of cores, potentially causing delays

Wrap-up

• The appropriate method should be adopted depending on the situation

  • ex)

    • When heavy traffic occurs due to increased visitors, Scale-out is more effective and also cheaper

    • For OLTP (Online Transaction) that requires frequent database updates, Scale-up is more effective