rblinne@ncrwic.Wichita.NCR.COM (Richard Blinne) (04/27/89)
My manager is working on a maintenence study for our Apollos and needs to know the mean time between failures for various different types of Apollos. Does anyone know the MTBFs for Apollo 3000, 3500, 4000, and 4500s. Thank you. Rich Blinne, NCR E&M Wichita
dennis@PUMPKIN-PATCH.NOSC.MIL (Dennis Cottel) (04/28/89)
Rich Blinne asked: > My manager is working on a maintenence study for our Apollos and > needs to know the mean time between failures for various different > types of Apollos. Does anyone know the MTBFs for Apollo 3000, 3500, > 4000, and 4500s. Thank you. Last year in response to a similar internal request, I put together the following note. My feeling is that things have been at least as good -- maybe better -- since then. --Dennis Dennis Cottel Naval Ocean Systems Center, San Diego, CA 92152 (619) 553-1645 dennis@nosc.MIL sdcsvax!noscvax!dennis -------------------------------------------------------------------------- Hardware reliability summary for DN3000/DN4000 machines. July 13, 1988 -------------------------------------------------------------------------- We have 20 DN3000s and 1 DN4000. We now have 266 node-months of use out of these machines. I ignored hardware calls that were made during the first few weeks which seemed to have to do with getting the machine working right in the first place. We have had 13 hardware failures: 4 displays replaced 1 display controller card replaced 2 noisy disks - fixed without replacing disks * 2 tape controller cards loose * 1 power supply replaced 1 tape drive replaced 1 disk controller card replaced 1 new battery The MTBF is therefore about 20 node-months. If you don't count the *starred items above which were not really hardware failures in that nothing had to be replaced, then there are 9 broken pieces over the 266 node-months -- pretty close to three years MTBF.
danny@idacom.UUCP (Danny Wilson) (04/29/89)
In article <5105@ncrwic.Wichita.NCR.COM>, rblinne@ncrwic.Wichita.NCR.COM (Richard Blinne) writes: > Does anyone know the MTBFs for Apollo 3000, 3500, > 4000, and 4500s. Thank you. I would also like to know this information and if possible, a comparision between the above Apollo nodes and the reliability information for Sun. BTW, according to reliability theory, MTBF (mean time Between failures) is not as meaningful as MTTF (Mean time to failure). --------------- ------------------ | | | |<-- MTTF --->|<- MTTR ->| | | | --------| |----------| <------ MTBF ----------> Therefore the MTBF actually should include the MTTR (mean time to repair). Manufacturers that are not aware seldom make this distintion, and when quoting MTBF information they actually are telling you MTTF!! In the exciting world :) of reliability theory (and for those military type guys), MTTF is the measure of choice. i.e. how long will it run. eg. A system could have a MTBF of 50 000 hours, however, it is a bad system if the MTTR is actually 48 000 hours!! Caveat Computor -- Danny Wilson IDACOM Electronics danny@idacom.uucp Edmonton, Alberta alberta!idacom!danny C A N A D A
dennis@peanuts.nosc.mil (Dennis Cottel) (05/02/89)
In article <639@idacom.UUCP> danny@idacom.UUCP (Danny Wilson) writes: >BTW, according to reliability theory, MTBF (mean time Between failures) >is not as meaningful as MTTF (Mean time to failure). > --------------- ------------------ > |<-- MTTF --->|<- MTTR ->| > --------| |----------| > <------ MTBF ----------> >Therefore the MTBF actually should include the MTTR (mean time >to repair). We have the standard Apollo maintenance contract, and our mean time to repair hardware problems has been measured in hours. For example, last week I made a call to the Apollo hotline at 0930 and the node was repaired by 1115. This is typical of the service we have been getting. The CE (Chris Evans, San Diego office) even apologized for being late! --Dennis Dennis Cottel Naval Ocean Systems Center, San Diego, CA 92152 (619) 553-1645 dennis@nosc.MIL sdcsvax!noscvax!dennis