Web Hosting Talk : Web Hosting Main Forums : Colocation and Data Centers : Power Question

[DPI]

Ok ok,

So, the DC is going to be giving me 10Amps of power for my 1/2 cabinet.

Isn't an amp how much current is flowing? How do I know how many servers I can put on that? is there some sort of formula?

[KarlZimmer]

Well, if you're using 120V power that is 1200 watts as it is V * A = W

With 10A you might be able to fill the half cab with 2u boxes, if you're lucky, but you'll never come close to filling it with 1u boxes.

[IRCCo Jeff]

Its quite possible to fill a half cab on 10A with 1U servers. Just because a PSU is rated at 350W, for example, does not mean that it will draw that much power.

Just make sure you use an APC that will sequence your ports so they dont all power up at once as this will likely cause you to blow a fuse

[KarlZimmer]

Originally posted by NSCNAP Jeff
Its quite possible to fill a half cab on 10A with 1U servers. Just because a PSU is rated at 350W, for example, does not mean that it will draw that much power.

Just make sure you use an APC that will sequence your ports so they dont all power up at once as this will likely cause you to blow a fuse

Could you tell me where you're finding these 1u servers that use 0.5A? I've generally noticed usage of roughly 1A, giving some room for error and additional load, per server, so in a half rack that is 20 1u servers thus 20A, roughly.

[Rusty500]

We typically see about 1.2A for Intel Pentium 4 3Ghz machines with 2 hard drives / RAID. Of course we see +/- .5A or so during bootup and heavy usage. I'd say 1.2 is probably the average, though.

[rackguru]

I've seen many, many, many 1U IDE single drive based systems run at under .5 amps. I've also seen many, many, many 1U Dell SCSI 3 disk systems run at over 1 amp. It depends on your setup, plain and simple. Also will you be running a switch? What type? 1U cisco? 2U summit (draws about 3x the power as a 1U cisco 3548), etc.

Too many factors. Get a baytech RPC-3 or an APC powerstrip that gives you usage read outs. It's about, oh, 1000 times easier to order power when you know you are running out, than running out (breaking the circuit) and trying to figure out what to do next.

[gilbert]

at least if you fill that half cabinet with 1 u servers would be able to seperate your servers /data and processes

which esentially increases security and the flow of things

[gbjbaanb]

You coudl always try to fill your cabinet with low-power CPUs, not necessarily the low-end ones either, the new Winchester AMD 64s are very power-lean, whereas the AMD AthlonXPs are very power-hungry, even when idle.

There was a test on Tom's Hardware recently about this, (testing P4s E0 Prescotts). The new AMDs used 3W at idle (athlon 2500+ used 30-something).. here's the link: http://www6.tomshardware.com/cpu/200...m4_570-20.html

[IRCCo Jeff]

KarlZimmer,

I was building them mostly (and some of them came from Rackmounts Etc.). The engineers at Limelight can attest to the setup I had before the NSCNAP buyout; several cabinets packed to the gills with mostly 1U and 2U servers on 15A feeds to each cabinet.

[KarlZimmer]

Originally posted by NSCNAP Jeff
KarlZimmer,

I was building them mostly (and some of them came from Rackmounts Etc.). The engineers at Limelight can attest to the setup I had before the NSCNAP buyout; several cabinets packed to the gills with mostly 1U and 2U servers on 15A feeds to each cabinet.

That is definitely impressive then, not much load on the boxes then? What hardware configurations in those? If I could be looking at 0.5A or so per box I could save some serious money on power... Though I think the dual Xeon boxes could be affecting the average more than I thought.

[IRCCo Jeff]

Karl,

Dual Xeon's will definately draw significant power, to the extent where those 40A handoffs you have will come in handy . In my example, only one or two of the boxes in question were Xeon. The rest were Celeron's and P4's.

[superbservers]

For a dual CPU server (Xeon), plan for 1.8 - 2.4 Amps. For a single CPU server (P4), plan for 1.4 - 1.8 Amps. the power use depends on the server load. This is the power use at full load, but not at boot-up (at boot up it is still slighlty higher).

It will vary depending on the board, power supply, how many hard drives and other things are present in the server, etc., but this is the general range to expect.

So really, on 10 Amps you can fit about 5 current servers. If you have older generation ones (year+ old, older run CPUs or Celerons), then perhaps up to 10 or even 11 or 12 (safely, w/o tripping the 10A power breaker, presuming there is one).

[IRCCo Jeff]

Admittedly I do not know much about Xeon power consumption, but I guarentee you're way off on that P4 estimate.

Anyone who wants to try this at home: A typical feed shared between two bedrooms in a typical American household is 15A (you can go look on your circuit breaker to make sure). Try plugging in a bunch of computers and see where the threshold lies

[Kevin Teoh]

Compare it to old apartments that still use rated fuses--my apartment only allows 20A total...imagine if your computer used up a lot? So much that you couldn't run other appliances

[superbservers]

These are accurate measures measured by two different parties using different power measurement devices. That is based on the configuration of servers that we use. Naturally, different configurations will yield different results (e.g. older CPU generations use less power, less or different brand and capacity hard drives mean less power, different board, power supply, etc. - it all makes a significant difference).