Hello NANOG group. I am trying to make a case for using DC power supplies versus AC power supplies for typical IP networking equipment. Is there any published whitepapers detailing this subject? Do you have any suggestions to aide my argument? _____________________________________________________________ Get your own free Ranch eMail and Classified Ads at http://cattletoday.com _____________________________________________________________ Select your own custom email address for FREE! Get you@yourchoice.com w/No Ads, 6MB, POP & more! http://www.everyone.net/selectmail?campaign=tag
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. Also, some hardware only is available in DC form such as the ons15454's I believe. ----- Original Message ----- From: "ip dude" <ipdude@cattle-today.com> To: <nanog@merit.edu> Sent: Friday, December 27, 2002 5:14 PM Subject: DC power versus AC power
Hello NANOG group. I am trying to make a case for using DC power supplies
versus AC power supplies for typical IP networking equipment. Is there any published whitepapers detailing this subject? Do you have any suggestions to aide my argument?
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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_________
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 - --On Sunday, December 29, 2002 00:46:56 -0500 jlewis@lewis.org wrote:
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?
We've built a number of "joiner" boxes in-house at KTHNOC; basically an aluminium box with rectifier bridge and heatsink, and screw terminals. We use them for 2511 terminal servers and similar. So, yes.
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.
YMMV, but 4 times 2x10mm² + 16mm² PE (The DC connects for a 12n16 GSR) I find bulkier than 4 10A power cords ;-). You are right on spot about the tidy/sturdy part, though. - -- Måns Nilsson Systems Specialist +46 70 681 7204 KTHNOC MN1334-RIPE We're sysadmins. To us, data is a protocol-overhe -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.7 (OpenBSD) iD8DBQE+D2P802/pMZDM1cURAmCfAJ9lumFsIw0n1ZrUjWLg0/Fy1gC2/QCgm2/F NvqZ52RiOzlYKY+ul2YF3lI= =O9Am -----END PGP SIGNATURE-----
Thus spake ip dude <ipdude@cattle-today.com>:
Hello NANOG group. I am trying to make a case for using DC power supplies versus AC power supplies for typical IP networking equipment. Is there any published whitepapers detailing this subject? Do you have any suggestions to aide my argument?
Most of the argument depends on the facility you're in. Assuming you're asking as an end-customer: DC requires clue from your staff when installing/removing equipment, and this means safety training at a minimum. Power choice also affects your equipment purchasing: DC versions of gear are often priced higher, and gear not intended for telcos/ISPs may not have a DC option available at all. OTOH, many colos -- especially ones run by telcos -- don't provide AC UPS. If you want AC UPS in these environments, you'll have to provide your own, which is expensive, bulky, and a maintainance burden. If you're building your own datacenter, please specify that and I'm sure you'll get a whole different discussion :) S
For those AC only powered units, you can also purchase an invertor for DC to AC conversion. You would then have the advantages of DC for your AC equipment. This does, however, add the potential of another point of failure such as fuses or breakers in the invertor. ----- Original Message ----- From: "Stephen Sprunk" <ssprunk@cisco.com> To: <ipdude@cattle-today.com>; <nanog@merit.edu> Sent: Sunday, December 29, 2002 1:58 AM Subject: Re: DC power versus AC power
Thus spake ip dude <ipdude@cattle-today.com>:
Hello NANOG group. I am trying to make a case for using DC power supplies versus AC power supplies for typical IP networking equipment. Is there any published whitepapers detailing this subject? Do you have any suggestions to aide my argument?
Most of the argument depends on the facility you're in. Assuming you're asking as an end-customer:
DC requires clue from your staff when installing/removing equipment, and this means safety training at a minimum. Power choice also affects your equipment purchasing: DC versions of gear are often priced higher, and
gear
not intended for telcos/ISPs may not have a DC option available at all.
OTOH, many colos -- especially ones run by telcos -- don't provide AC UPS. If you want AC UPS in these environments, you'll have to provide your own, which is expensive, bulky, and a maintainance burden.
If you're building your own datacenter, please specify that and I'm sure you'll get a whole different discussion :)
S
Thus spake "Wayne Bogan" <wbogan@InfoAve.Net>
For those AC only powered units, you can also purchase an invertor for DC
to
AC conversion. You would then have the advantages of DC for your AC equipment. This does, however, add the potential of another point of failure such as fuses or breakers in the invertor.
Well, that's how AC UPS's work -- just beware what percentage of the input current is lost in the conversion from DC to AC, plus what is lost converting from AC back to DC inside the equipment. Much simpler to specify DC equipment to begin with if you really care about availability. S
participants (6)
-
ip dude -
jlewis＠lewis.org -
Måns Nilsson -
Scott Granados -
Stephen Sprunk -
Wayne Bogan