SRC Forum - Message Replies
Forum: Reliability & Maintainability Questions and Answers
Topic: Reliability & Maintainability Questions and Answers
Topic Posted by: Reliability & Maintainability Forum
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998
Posted by: D. Gordon
Organization:Reliability Center, Inc.
Date posted: Thu May 10 13:25:06 US/Eastern 2001
Subject: Calculating Availability for Computer Systems
I have been searching for information about calculating availability for computer systems. When systems integrators carry out contracts they often have a system availability target of perhaps 99.8%. The people in companies who justify the figures perhaps use different methods of calculation from one company to another.
An example would be an Allen Bradley PLC system with 100 different modules that have quoted MTBFs, the system has some redundancy etc, what is the overall availability.
Standards exist (eg bellcore) for calculating reliability of components and cards etc, but when it comes to whole systems there doesn't seem to be any real consistancy and scarce information.
Please can you suggest the most comprehensive way of compounding the MTBfs of multipule components to attain an overall availability figure.
Reply Posted by: Barry Ma
Organization: Anritsu Company
Date Posted: Thu May 24 12:56:32 US/Eastern 2001
"MTTR is the mean time to repair each failure", said Bruce Dudley in his reply "Availability" 5/19/2001.
This is a very clear and concise definition of MTTR, as opposed to many others. Thank you, Bruce.