FYI Netflix is down
rbf+nanog at panix.com
Sun Jul 1 00:08:51 UTC 2012
On Sat, Jun 30, 2012 at 01:19:54PM -0700, Scott Howard wrote:
> On Sat, Jun 30, 2012 at 12:04 PM, Todd Underwood <toddunder at gmail.com>wrote:
> > This was not a cascading failure. It was a simple power outage
> > Cascading failures involve interdependencies among components.
> Not always. Cascading failures can also occur when there is zero
> dependency between components. The simplest form of this is where one
> environment fails over to another, but the target environment is not
> capable of handling the additional load and then "fails" itself as a result
> (in some form or other, but frequently different to the mode of the
> original failure).
That's an interdependency. Environment A is dependent on environment B
being up and pulling some of the load away from A; B is dependent on A
beingup and pulling some of the load away from B.
A Crashes for reason X -> Load Shifts to B -> B Crashes due to load
is a classic cascading failure. And it's not limited to software
systems. It's how most major blackouts occur (except with more than
three steps in the cascade, of course).
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