Key Characteristics of Distributed Systems

Scalability

• The capability of a system to grow and manage increased demand.
• A system that can continuously evolve to support growing amount of work is scalable.
• Horizontal scaling: by adding more servers into the pool of resources.
• Vertical scaling: by adding more resource (CPU, RAM, storage, etc) to an existing server. This approach comes with downtime and an upper limit.

Reliability

• Reliability is the probability that a system will fail in a given period.
• A distributed system is reliable if it keeps delivering its service even when one or multiple components fail.
• Reliability is achieved through redundancy of components and data (remove every single point of failure).

Availability

• Availability is the time a system remains operational to perform its required function in a specific period.
• Measured by the percentage of time that a system remains operational under normal conditions.
• A reliable system is available.
• An available system is not necessarily reliable.
  • A system with a security hole is available when there is no security attack.

Efficiency

• Latency: response time, the delay to obtain the first piece of data.
• Bandwidth: throughput, amount of data delivered in a given time.

Serviceability / Manageability

• Easiness to operate and maintain the system.
• Simplicity and spend with which a system can be repaired or maintained.