--- Richard A Steenbergen <ras@e-gerbil.net> wrote:
2x the hardware means 2x the number of hardware failures. It also means 2x the number of software upgrades, and probably some multiplier greater than 2x for the increased complexity and opportunity for software to go wrong. Dual routers just increases the number of overall failures in exchange for hoping that only one goes down at any given time.
The fallacy here is that the greater number of failures which a dual-router scenario will encounter are of the same Qualitative type as the failures your single router will encounter. This is clearly not true: one of a pair failing means that there will be a period of convergence, and then the remaining router will carry the load. If a single router fails, the load will not be carried until the router can be restored.
On one side of the coin, Cisco has done a masterful job at convincing the networking industry that the correct answer to their routine failures is to purchase double of everything. On the other side... Show me the box that never goes down. :)
My point exactly: from a design perspective it's much simpler to have a single box, but I have not seen single boxen which don't fail. I'm actually a big fan of the "cold-spare" approach: you preserve your simplicity, and any outage only lasts as long as it takes to unplug and re-plug... ===== David Barak -fully RFC 1925 compliant- __________________________________________________ Do you Yahoo!? Yahoo! Tax Center - File online, calculators, forms, and more http://tax.yahoo.com