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