Talk:Myth of the nines
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This article was nominated for deletion on June 29, 2006. The result of the discussion was keep. |
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[edit] Inconvenient outages
"Another factor is that computer systems do actually tend to experience outages at the most inconvenient time, when the system is most heavily used." Source? Crid 07:36, 16 December 2005 (UTC)
- Murphy's law?
Seriously, though, it's rather obvious that systems under heavy load are more prone to failure than systems under light load, because heavy loads exercise boundaries of system tolerances (they run hotter, consume more memory, use more disk space, process many different inputs that may trigger pathological cases in software, etc.) Furthermore, a system under heavy load is most probably under heavy load because there's a lot of work to be done, so an outage at these times is more inconvenient than an outage at a time when the system is picking its nose.
Per Wikipedia:Guide to writing better articles#State the obvious, we could put a note in to this effect if this line of reasoning is not obvious. JRM · Talk 01:24, 22 December 2005 (UTC)- The insight is more implicit than obvious... The word "inconvenient" is what bugs me. Boolean logic is not concerned with what we feel is tolerable. Murphy's law is an attitude problem. But computer science is inherently technical and seems like black magic to many people. (That's why I got to this page.) So perhaps superstitious rhetoric should be avoided. Anybody who pursues 5 nines for a living is probably all about the real world. Anyway, I trust your judgment. Crid 01:24, 25 December 2005 (UTC)
- For completeness, the mention of Murphy's law wasn't supposed to be a rational explanation... I see what you mean, though, the sentence seems to appeal to a sort of mystic intuition about "how these things work" which is really not necessary; there are perfectly objective explanations for why systems fail at those times humans would consider most inconvenient.
- What's worse from a writer's point of view, however, is that the fact is irrelevant. It doesn't tie in with anything. It is not "another factor" (of what?), it's just a tidbit about subjective perception of failure. I've removed it on those grounds. JRM · Talk 00:31, 26 December 2005 (UTC)
- The insight is more implicit than obvious... The word "inconvenient" is what bugs me. Boolean logic is not concerned with what we feel is tolerable. Murphy's law is an attitude problem. But computer science is inherently technical and seems like black magic to many people. (That's why I got to this page.) So perhaps superstitious rhetoric should be avoided. Anybody who pursues 5 nines for a living is probably all about the real world. Anyway, I trust your judgment. Crid 01:24, 25 December 2005 (UTC)
[edit] What it means
delivering its service to the user 99.999% of the time it is needed.
No, no? I believe that 99.999% is a measure of the absolute number of minutes (or whatever) in a year; the phrasing we're using now isn't accurate for systems which must be usable as much as possible when the business is *not* in operation 24/7/365.25. --Baylink 18:13, 11 July 2006 (UTC)
[edit] Planned vs Unplanned downtime
I've heard someone say that contracts specifying nines of uptime typically exclude counting periods of "planned downtime", which could in fact extend into hours or days or longer as long as the outage is planned and scheduled. In such contracts, only "unplanned downtime" is usually considered to count against the alloted downtime. Can anyone else confirm this convention and maybe integrate into the article if this is indeed a common industry interpretation? -- Bovineone 20:59, 13 August 2006 (UTC)
[edit] Mathematics
Just to note explicitly a trivial point when calculating probability. We've all implicitly used the approximation that:
(1 + x)^n = 1 + n.x #for small x.
This is a very accurate approximation, but its use should be noted.
