On Jul 25, 2007, at 3:35 PM, Patrick W. Gilmore wrote:

On Jul 25, 2007, at 2:03 PM, Tuc at T-B-O-H.NET wrote:

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If they can be avoided, why do we put up with them? Do we really want our colo in downtown San Francisco bad enough to take the risk of having a single point of failure? How can we, as engineers, ask questions about how many generators, how much fuel, and yet take for granted that there is one button on the wall that makes it all turn off? Is it simply that having colo in the middle of the city is so convenient that it overrides the increased cost and the reduced redundancy that are necessitated by that location?

You forgot the default "Single Point of Failure" in anything..

HUMANS.

The earth is a SPoF. Let's put DCs on the moon.

Besides, safety always overrides convenience. And I don't think that is a bad trade off.

Me neither... Having multiple redundant sites (and a well designed network between them) is almost always going to be better than a single, wildly redundant site. No matter how much redundancy you build into a single site, you cannot (realistically) engineer away things like floods, etc. Planning your redundancy and testing it though is very important... Random anecdote (from a friend, I don't know if it true or not): Back in the day (before cheap international circuits), a very large financial in New York needed connectivity to some branches in Europe, so they bought some capacity on a satellite transponder and built their own ground-station (not cheap) fairly close to NY. They then realized that the needed a redundant ground station in case the first one failed or something similar, so the built a second ground- station, just outside Jersey City.... One of the satellite connectivity failure modes is... rain fade..... W

-- TTFN, patrick

-- "Does Emacs have the Buddha nature? Why not? It has bloody well everything else!"