Reliability vs availability: Understanding the differences

What is reliability?

Reliability is the likelihood that a system or component will perform its function without failure at any specific time. It also affects customers’ confidence in the technology.

Payroll systems, for example, must process direct deposits into bank accounts during a defined window on a specific day each month. A cold storage system must identify a power outage and automatically switch to backup generators. Every industry relies on critical, automated processes using unique incident management KPIs. Process failures can have a catastrophic effect on the bottom line.

How to measure reliability

You can measure reliability with standard incident management metrics, such as:

• Mean time between failures: Calculate this by dividing the total operation time by the number of failures.
• Failure rate: Calculate this by dividing the number of failures by the total time in service.

It’s important to consider additional factors, such as service level agreements and what customers expect from the system. Defining reliability standards can vary based on what’s at risk if a system fails. For example, will failure cause a group of tax preparers to take the afternoon off? Or will it strand thousands of airline passengers far from their homes?

How to improve reliability

There are a few steps businesses can take to improve service reliability:

• Create routine maintenance schedules to keep systems up-to-date and modernized.
• Implement system redundancy to prevent component failures from halting processes.
• Complete quality control and testing when upgrading or making system changes so teams can correct issues before they reach production.
• Improve incident communication to decrease response and recovery time.

What is availability?

Availability is the percentage of time that a system or component is operational and can perform its function—its up-time.

Large online retailers, for example, must maintain site availability 24/7 to meet customer demand or risk losing market share to competitors. Availability takes into account a variety of conditions, such as user internet speeds and peak traffic times. Loss of availability in crucial systems, such as neonatal intensive care monitoring, can even be life-threatening.  

How to measure availability

Measuring availability is a single percentage metric. It is the total elapsed time minus the total downtime divided by the total elapsed time:

availability percentage = (total elapsed time – downtime) / total elapsed time

For example, if an online retail site is down for three hours in a day due to traffic overload, its availability score is 87.5%. The standard may be closer to 99.5% for large international retailers, giving the online retailer much to improve. 

ITSM software such as Jira Service Management helps teams track incidents and collect data for measuring availability.

How to improve availability

There are several ways companies can improve availability:

• Implement proactive, standard maintenance schedules to ensure high availability.
• Add system redundancy with failover mechanisms.
• Create rapid repair processes as part of incident management.

Proactive maintenance, in particular, can help businesses gain greater availability and service reliability. Conducting a reliability, availability, and maintainability (RAM) study can provide important insights into where to focus maintenance efforts.  

Reliability vs. availability

Reliability and availability are often mistaken for the same thing. However, they not only differ but also don't always align.

Even the standards by which companies measure them can differ, depending on the system and its function. To gain an accurate view of any business system, you should analyze reliability vs. availability metrics separately.

• Reliability measures whether the system has delivered the correct output at a specific, defined time—e.g., transferring payroll funds to the correct accounts on the right day. 
• Availability measures the system’s up-time—for example, providing uninterrupted oxygen monitoring to premature babies during their necessary incubation period.

Jira Service Management includes automation templates that can collect data, elevate incident communication, and improve overall customer service.

Differences

Reliability vs. availability metrics and their differences become clear when considering how to use them to improve performance. Reliability aims to minimize system failures and downtime, while availability aims to maximize operational time.

Measuring the service reliability of a grocery self-checkout system may involve analyzing how often customers require clerk assistance to complete a transaction. Measuring availability may involve checking whether customers attempt self-checkout at all.

Similarities

Reliability and availability complement each other. Competitive businesses strive to improve both metrics for the best results. For example, systems with high availability but frequent reliability failures are unlikely to serve customer needs no matter how quickly you can resolve the failures.

Improving both areas often requires similar approaches, such as performing routine maintenance, adding redundancy, contingency planning, and testing.

Factors affecting reliability and availability

Several factors can affect system reliability and availability:

• Environmental: This can include IoT components, such as pressure gauges with exposure to inclement weather, or cyclical user patterns, such as high retail site traffic on specific days.
• Component quality: Examples include third-party integrations or hardware.
• Operational: This may include the frequency of inspections and maintenance or investment in modernized software.

Businesses can improve overall service reliability and availability by standardizing environmental thresholds and adding redundancy, requiring ISO compliance for component quality, or implementing procedures to inspect, test, and maintain every aspect of the system.

Balance reliability and availability with Jira Service Management

With the right tools and approach, companies can balance system reliability and availability, especially in our always-on world. Jira Service Management enables teams to restore service rapidly.

Jira Software and Jira Service Management empower customers to report issues and help service teams centralize alerts for rapid categorization and prioritization. Rules and communication channels ensure that no one ever misses a critical issue.

Learn more about Incident Management in Jira Service Management 

What is an example of reliability vs. availability?

Consider new technology like driverless cars. Service reliability standards are near or at 100% because a single failure can result in injury or death. 

Conversely, the availability of driverless cars affects the user experience. The higher the availability, or operational time, the better the experience. Low availability may cause the business to lose market share, but it is unlikely to result in injury or death.

Why are reliability and availability important?

Both reliability and availability impact a business’s bottom line because they affect customer satisfaction. In addition, systems that are not available or reliable cost companies money in lost revenue, spoilage, unplanned maintenance costs, and lost productivity.

Focusing efforts to increase service reliability and availability can result in a greater competitive advantage, an increased market share, better revenue, and an improved budgeting plan for maintenance costs.

What are the trade-offs between reliability and availability?

Businesses sometimes have to prioritize reliability over availability or vice versa. Real trade-offs may be necessary when timelines are short or investment funds are limited.

In the case of driverless cars, businesses are likely to invest more time and effort in increased reliability, even if it negatively impacts availability. However, in less critical situations, such as online retail, a business may focus on increasing availability because being “always open” is one of the key differentiators between e-commerce and brick-and-mortar competitors.