Distributed System Scalability Types: Knowing The Differences Can Mean Millions
Apr 16, 2022
Nowadays, more and more companies are embracing the idea of scalability. Some even choose to deploy a system that scales automatically. However, there are three major types of scalability, and this article will briefly explain each one.
What is a distributed system?
A distributed system is where parts of the system are spread out over a network. This can be done for performance or resilience reasons. There are different types of distributed systems, which we will cover in this article. Parts of a distributed system can be spread out over multiple computers, multiple devices, or even multiple locations. One common example of a distributed system in the world wide web, which is spread out over millions of computers around the world. Another example is a set of databases that are replicated across multiple servers for fault tolerance.
There are many benefits to using a distributed system. For example, distributing computational tasks across multiple computers can lead to better performance. When done correctly, distributing data across multiple devices can make the system more resilient to failures.
There are also some challenges that come with using a distributed system. One challenge is that distributing data and computation can add complexity. Another challenge is that distributing data and computation can introduce new sources of errors.
Despite these challenges, distributed systems are widely used because the benefits often outweigh the challenges. In many cases, using a distributed system can mean the difference between a successful project and a failed one.
Examples of Distributed Systems
There are several types of distributed systems, each with its own set of characteristics. Here are some examples:
Client-server systems: A central server manages and coordinates the work of a number of client computers. The clients request services from the server, which then provides them. This is the most common type of distributed system.
Peer-to-peer systems: There is no central server; instead, each computer in the system act as both a client and a server. This type of system is often used for file sharing and other applications where it is not necessary to have a central authority.
Grid systems: A grid system is a type of distributed system that uses a network of computers to share resources, such as storage or processing power. Grid systems are often used for scientific or business applications where large amounts of data need to be processed.
Cloud computing: Cloud computing is a type of distributed system that uses a network of computers to provide services, such as storage or applications, to users over the Internet.
Type of scalability we have in distributed systems
Type of scalability we have in distributed systems. A distributed system uses more than one computer to operate. These systems can scale in three main ways: size, geographical, and administrative scale. Size scalability refers to the number of nodes in the system, geographical scalability refers to the number of different locations where the nodes are located, and administrative scalability refers to the number of different organizations that manage the nodes.
In distributed systems, there are 3 main types of scalability: size, geographical, and administrative.
Size refers to the number of nodes in a system or network.
Geographical scalability refers to the number of different locations where the nodes are located (and where they have redundancy, failover, etc.).
Administrative scalability refers to scaling the system by adding more management policies or personnel.
So geographic and administrative scalability refers specifically to scaling out a sub-system, and size or computational scalability refers to scaling up a single computer (or node).
Size and computational scalability are independent of each other. In other words: if a problem can be solved using a 1000 node cluster, it will also work on one computer. However, with some problems, it is easier to scale out than to scale up, because that allows us to use commodity hardware. Problems that can be easily scaled out include distributed storage systems (such as HDFS), whereas problems that can be easily scaled up include numeric or scientific computing applications.
In some cases, we are interested in a given cluster reaching a certain level of size or computational power and then staying there, without any further increase. This is the case for example with a private cloud platform (such as Google App Engine), where we want to make sure that the capacity of the underlying hardware is sufficient and does not need to be upgraded periodically. In other cases, we want to make sure that the cluster size stays within certain bounds. For example, with Hadoop’s Capacity Scheduler, we can specify a minimum and a maximum number of machines for a given job to be accepted.
In general, scalability measures can be classified into two broad categories: capacity/scale-up measures (which are applicable to clusters with a fixed topology) and density/scale-out measures (which are applicable to clusters where new nodes can be added).
The CAP theorem
The CAP theorem is one of the most important concepts in distributed systems. It states that it is impossible for a distributed system to have all three of the following properties:
Consistency: All nodes in the system see the same data
Availability: Every node in the system can be reached and is responsive
Partition tolerance: The system can continue to operate even if there is a network partition (i.e. some nodes are unreachable)
The CAP theorem has implications for how we design and build distributed systems. For example, if we want our system to be consistent, then we need to be aware of the trade-offs that come with that decision. We may need to sacrifice availability or partition tolerance in order to achieve consistency.
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