Not quite as simple Jonah.... CO equipment is designed for 48v for many
reasons. It's also designed to deal with concrete floors, inefficient
HVAC, dust, etc.
Unfortunately, a modern megapop consists of a lot of interesting
equipment that doesn't come in 48v DC versions. Alpha 8400s, Large SGIs,
and server like things (yeah, I know, there are companies who make
retrofit kits for some of them, but they're not standard).
The real issue is planning... MAE E and MAE W *weren't* designed for the
things that MFS is stuffing in them. Most of the other pops have the
same problem. It *is* possible to design a facility that is run off an
inverter permanently, which is connected to a UPS, which is connected to
utility power, and to a diesel generator, which *is* able to cope with
extended failures of _utility power_ without affecting the equipment
(routers, switches, modems, and servers) at all. And I think the modern
facilities will be built that way. 4-12 hours of batteries is serious
when you're talking about a large hosting facility. Sprint/MCI may be
laughing, but they're haveing to scramble to build POPs capable of
supporting server farms because they can't do that now.
And another thing, batteries or not, *no-one* can easily survive a
catastrophic event like a fire, an explosion, or even the wires that got
eaten in BBNs Stanford center last year. (Didn't AT&T hose most of
Chicago's loop area a few years ago, for more than a *week*?) I bet they
had DC in their vault. Didn't help them much...
Rodney Joffe
Genuity Inc., a Bechtel company
http://www.genuity.net
It's also designed to deal with concrete floors, inefficient
HVAC, dust, etc.
This is interesting, as we have two colo sites now... One fits the
description above (somewhat), and one fits the description below...
It *is* possible to design a facility that is run off an
inverter permanently, which is connected to a UPS, which is connected to
utility power, and to a diesel generator, which *is* able to cope with
extended failures of _utility power_ without affecting the equipment
(routers, switches, modems, and servers) at all. And I think the modern
The site where we locate our dialup equipment (ACC-Old Slip) is old-school
telco. All 48V, all battery backed-up if you take the DC feed. It's brand
new, but it does not have a raised floor, just overhead channels for all
the telco wiring... They thought we were crazy when we asked for AC, but
when told how many amps a USR TCH draws, they happily brought more AC to
us. We're backed up by a generator, but that's it. During the time it
takes to crank it up, we're dead.
Now at Telehouse NY, (our cabinet being right across from Genuity, btw)
they tell us that all power is coming from an inverter, and there is
enough battery power to keep the entire facility going until the generator
comes online. They even invite you to come out and see them
disconnect the utility co. power during their quarterly tests... This is
primarily a "datacenter" with a much higher count of things that say
"Cisco" on them than those that say "Lucent" or "AT&T". They also claim
they have 3 days of diesel fuel available...
So I guess the rule here is, put your 48V stuff at a telco colo, and put
the big AC stuff at a modern datacenter...
Charles
~~~~~~~~~ ~~~~~~~~~~~
Charles Sprickman Internet Channel
INCH System Administration Team (212)243-5200
spork@inch.com access@inch.com
Use invertors off your -48VDC plant for your AC equipment.
An AC UPS:
AC feed from electric co --> rectifier --> DC batteries --> inverters
I have yet to see an AC UPS with a longer runtime than 2hours (100KW+)
with full battery options installed. Exide/Liebert make excellent UPS
systems, but they are _not_ meant for extended runtime. Instead they
are meant for a graceful shutdown of all systems when extended power
outages occur.
Jonah
Now at Telehouse NY, (our cabinet being right across from Genuity, btw)
they tell us that all power is coming from an inverter, and there is
enough battery power to keep the entire facility going until the generator
comes online. They even invite you to come out and see them
disconnect the utility co. power during their quarterly tests... This is
primarily a "datacenter" with a much higher count of things that say
"Cisco" on them than those that say "Lucent" or "AT&T". They also claim
they have 3 days of diesel fuel available...
How long does it take your generator to kick in? IMO you had _better_
have 4hours of battery plant *MINIMUM* in case your generator does not
start. The 4hours is needed so you can get your rollup generator (from
a generator contractor) drive to your pop and hooked into your
external power tap. We have a 225KW Onan that goes from off to fully
operational in 5seconds. Its tested (non-loaded) every monday, and
tested with full load every 4th monday. I have seen a _lot_ of
generator problems.
So I guess the rule here is, put your 48V stuff at a telco colo, and put
the big AC stuff at a modern datacenter...
huh? Every modern datacenter I have seen is running -48VDC. Are you
aware of how much electrical interference AC power causes? Your
equipment _all_ runs on DC power. The AC power supplies in your
equipment is just rectifying the power from AC --> DC (usually 5v or
12v DC). By running AC power backup systems, you are losing ~20-30%
effiency due to power conversions.
Jonah