On Sat, Jun 30, 2012 at 01:19:54PM -0700, Scott Howard wrote: > On Sat, Jun 30, 2012 at 12:04 PM, Todd Underwood <toddun...@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