On Fri, 27 Dec 2002, Scott Granados wrote:
It is likely that in many settings during power failures transition from ac street power to ac generator power will have some lag and during that time your hardware could loose power. This of course depends on ups systems in use and many factors. Dc usually however is clean in its transition and goes with out saying is battery backed up.
I'll add to that, that since DC removes the need for your own UPS's, by going with DC, you save rack space, deploy less gear (UPS's are HEAVY), and don't have to worry about which POPs have how many UPS's with dead batteries at any given time. OTOH, since with DC you're unlikely to have any backup power of your own, it is important to wire up both an A side and B side. Some places (like certain telcos) like to briefly turn off parts of their DC power grids somewhat regularly. This makes gear with only one set of DC inputs rather annoying. Does anyone actually wire up both the A side and B side to a single DC power supply and use diodes to keep the two supply grids separate? DC also avoids bulky AC power cords...and not only are the wires less bulky, but you'll likely cut them to the actual length needed. Since DC wiring is usually screwed down, they don't get bumped or accidentally pulled out of the outlets as often. ---------------------------------------------------------------------- Jon Lewis *jlewis@lewis.org*| I route System Administrator | therefore you are Atlantic Net | _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________