Advanced Wireless Communication and Tracking Tutorial: 4. Survivability, Reliability, and Availability
CDC / National Institute for Occupational Safety and Health · National Institute for Occupational Safety and Health (NIOSH)
This chapter of the NIOSH mining communications tutorial separates system reliability, survivability and availability, and illustrates repairable availability with series and parallel configurations.
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Overview
The chapter's main contribution is to separate three concepts: reliability (operating without failure over a mission), survivability (continuing to function after an event) and availability (being operational at any given moment). They are often confused in data centers too: 99.99% availability does not rule out one long outage. A single long outage and many short ones can give the same annual percentage but very different operational consequences.
For a repairable system, availability is estimated as MTBF divided by (MTBF + MTTR), so the result depends on both the failure interval and the repair duration. For instance, an MTBF of 1,000 hours and an MTTR of 10 hours gives availability of about 0.990; this is a simple application of the formula, not the document's own number. The chapter also uses diagrams to show how series and parallel configurations affect availability.
The limit is that the equations are general examples and the operating context is underground communications; there is no data-center failure data. An availability estimate should be kept distinct from mission reliability and verified operational uptime, with the failure and repair assumptions behind it stated. Survivability describes continued function after an event; in a data center the equivalent is the rest of the system continuing to run when one zone is lost.
Key points
- The document treats system reliability, survivability and availability as distinct concepts.
- Repairable availability is estimated as MTBF / (MTBF + MTTR).
- The result depends on both the failure interval and the repair duration.
- Series and parallel configurations are illustrated through availability.
- The context is underground mine communications; the equations are general examples.
Using it in design
- Write the MTBF and MTTR assumptions beside every availability estimate.
- Show availability as a metric separate from mission reliability and verified operational uptime.
- Tie MTTR to inputs such as spares and response time and show the sensitivity.
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Who should read it
Designers who calculate an availability figure and must explain what that figure does and does not prove.
Publication details
- Authors
- National Institute for Occupational Safety and Health (NIOSH)
- Publisher
- CDC / National Institute for Occupational Safety and Health
- Year
- 2019
- Document number
- Tutorial chapter 4
- Document language
- English
- Source type
- Government / public
- Access
- Free to read
- Licence
- Copyright retained; citation only — the publisher’s terms apply to the original document
Citation
National Institute for Occupational Safety and Health (NIOSH) (2019). Advanced Wireless Communication and Tracking Tutorial: 4. Survivability, Reliability, and Availability. CDC / National Institute for Occupational Safety and Health. Tutorial chapter 4. https://archive.cdc.gov/www_cdc_gov/niosh/mining/content/emergencymanagementandresponse/commtracking/advcommtrackingtutorial4.html
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