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From Mark Brouwer <mark.brou...@cheiron.org>
Subject Re: Concurrency and River
Date Tue, 02 Oct 2007 14:23:15 GMT
Rick Moynihan wrote:

> It's claimed that these properties have led to Erlang systems being 
> created with 99.9999999% (9 9's) reliability.

Marketing at its best :-) From the Armstrong thesis: "For the Ericsson
AXD301 the only information on the long-term stability of the system
came from a power-point presentation showing some figures claiming that
a major customer had run an 11 node system with a 99.9999999%
reliability, though how these figure had been obtained was not
documented."

In his case studies chapter he mentions there have been various process
crashes although they have been able to upgrade the code to fix those
problems, and I must admit this is certainly impressive. Some
characteristics (just functions) in Erlang makes upgrading of code so
much easier than e.g. is possible with classes in Java.

I haven't come to the part yet where they show how to transfer 'state'
contained by a crashed or broken process to one that is going to use
fixed code or where data structures significantly changed. I won't be
disappointed though when it turns out there are some limitations about
what can be achieved, because in general when people have surgery they
are suspended as well.
-- 
Mark





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