dual router vs. single "reliable" router

Thu Apr 10 17:04:50 UTC 2003

Thus spake "Richard A Steenbergen" <ras at e-gerbil.net>
> Throw in some assumptions (which may or may not be true, I'll agree
> that some of their numbers are a little "off") that every one of those
> failures involves some service impact, you could easily make a case
> that one box which doesn't go down is better than two boxes which
> routinely go down.

If a tree falls down in a forest, but service isn't affected, do we care if
the tree falling made a noise?  If you have two devices which are up 99% of
the time, then one of the two is up 99.99% of the time.  While designing
with two of everything is indeed more complex, it's often simpler than
designing a single product that's more reliable.

Having two of everything also simplifies maintenance, since you don't care
(much) about an individual box being down.  Public ATM networks are hell to
maintain because every node must be up 24x7 and simple things (to
routerheads) like a software upgrade are a 3+ month project because it must
be done online without dropping a single cell.

S

Stephen Sprunk         "God does not play dice."  --Albert Einstein
CCIE #3723         "God is an inveterate gambler, and He throws the
K5SSS        dice at every possible opportunity." --Stephen Hawking