[154291] in North American Network Operators' Group
Re: FYI Netflix is down
daemon@ATHENA.MIT.EDU (Brett Frankenberger)
Sat Jun 30 20:09:31 2012
Date: Sat, 30 Jun 2012 19:08:51 -0500
From: Brett Frankenberger <rbf+nanog@panix.com>
To: Scott Howard <scott@doc.net.au>
In-Reply-To: <CACnPsNVHpp4T9q7vufjM0L9rSo3FJJaxpd1XY3UDAYjZ9RpZKA@mail.gmail.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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@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).
-- Brett
