For example, if two components are arranged in parallel, each with reliability R 1 = R 2 = 0.9, that is, F 1 = F 2 = 0.1, the resultant probability of failure is F = 0.1 × 0.1 = 0.01. The resultant reliability is R = 1 – 0.01 = 0.99.

So, to realize these benefits of being reliable, here are five simple actions you can take.

1. Manage Commitments. Being reliable does not mean saying yes to everyone.
2. Proactively Communicate. Avoid surprises.
3. Start and Finish.
4. Be Truthful.
5. Respect Time, Yours and Others’.

The measurement of Availability is driven by time loss whereas the measurement of Reliability is driven by the frequency and impact of failures. Mathematically, the Availability of a system can be treated as a function of its Reliability. In other words, Reliability can be considered a subset of Availability.

To calculate MTBF, divide the total number of operational hours in a period by the number of failures that occurred in that period. MTBF is usually measured in hours. For example, an asset may have been operational for 1,000 hours in a year. Over the course of that year, that asset broke down eight times.

Calculating system availability System availability is calculated by dividing uptime by the total sum of uptime and downtime.

Reliability can be defined as the probability that a system will produce correct outputs up to some given time t. Availability means the probability that a system is operational at a given time, i.e. the amount of time a device is actually operating as the percentage of total time it should be operating.

As a result, there are a number of different classifications of availability, including:

• Instantaneous (or Point) Availability.
• Average Uptime Availability (or Mean Availability)
• Steady State Availability.
• Inherent Availability.
• Achieved Availability.
• Operational Availability.

Where availability measures the percentage of locations that can successfully reach your server, Uptime measures whether the server is reachable at all. Uptime is calculated, in each test interval, as either 100% if one or more locations can successfully reach the server, or 0% if none can.

It’s generally understood that 99.9% uptime is a hosting industry standard, whereas five nines or better (99.999% and up) is the ideal. 99.9% uptime means your website may be down for a total of eight hours, 45 minutes, and 57 seconds each year.

If your business uses a service with a 99% uptime guarantee that means you should expect: 14 minutes, 24 seconds of downtime every day; 1 hour, 40 minutes and 48 seconds of downtime every week; 6 hours, 43 minutes and 12 seconds of downtime every month and.

High Availability (HA) describes systems that are dependable enough to operate continuously without failing. They are well-tested and sometimes equipped with redundant components. High availability refers to those systems that offer a high level of operational performance and quality over a relevant time period.

99.999%