Availability and Reliability Differences

Reliability Availability Serviceability

Although they are different in detail.

Availability: Pay attention to failure time/total time, number of failures/total number of times

Reliability: The longer it takes to measure the first failure after startup, the better.

Generally improves reliability while also improving usability.

Reliability and availability are our common IT system metrics, and friends ask me what the difference is between the two indicators, but I also have a concept. No authoritative documents for a moment, Google did not find any precise definition, can only say my understanding, my general impression is: Reliability (R) is the probability of a normal operation from the time it starts running to a certain moment. The average value of the time between two faults that the system can work normally becomes the average trouble-free working time. The average repair time is usually used to indicate the maintainability of the computer (S); Reliability is the probability that the system can perform its functions correctly at a given time interval and under given conditions. Availability (A) is the probability that the system will function properly at any point in the execution of a task. A= mttf/(mttf+mttr) *100% MTTF+MTTR=MTBF (Mean time between Failure) Increased reliability requires an emphasis on reducing the number of system outages (failures) and increasing availability needs to emphasize reducing the time to recover from disasters. A system 10 times a year due to failure, each recovery on average 20 minutes, B system due to failure 2 times a year, 5 hours each time to recover. The availability of a system is higher than the B system, but the reliability is worse than the B system. The quantitative index of reliability is the average fault-free running time of the system, and the quantization index of usability is the total time of the system failure-free operation in the period. To improve reliability, management and technical means such as change management, Ups,raid,cluster, and link redundancy can be used to reduce the likelihood of system down. To improve availability, in addition to increased reliability, you can use reasonable backups, business continuity plans, and so on to reduce the time it takes to recover from a disaster. Precise description of availability and reliability differences: http://wenku.baidu.com/view/de6090bbfd0a79563c1e72a6.html

Transferred from: http://huxl007.blog.163.com/blog/static/12018678820095189478678/