I recently moved the servers for dvorak.org to a new data center (Hurricane Electric) where the cabinets have only 15 amps of current available. At the time I thought that this would be plenty of power to run my 7 computers but as it turns out it wasn’t. The first day I tripped the breaker on the power strip they provide in the cabinet.
As it turns out the power strip breaker was a little too sensitive but I was pulling around 12-14 amps during morning rush hour when the spam filtering peaks. I had thought I could easily run 10 computers there but it turned out that my computers pull more than I thought. One computer was an older computer that I really wasn’t using anymore and I pulled it out, but I needed to run more that 6 computers. So I had to figure out a way to cut my power usage.
I did some research and I found ways to cut the power usage dramatically. So if any of you are running computers in a data center or are just wanting to save some money on your electric bill, here’s some tips to make your computer a little greener.
The first thing I did was get a power measuring meter. The device pictured above is called a KILL-A-WATT and is sold at NewEgg for $18. This is a must have toy for measuring the power usage of anything up to 15 AMPS.
Here are 3 different power saving techniques I tested.
- High Efficiency Power Supply
- AMD Cool and Quiet (Intel Speedstep equivelent)
- Power Saving OS (New Kernels vs. Old Kernels)
My test computer is an Asus motherboard running a dual core Athlon 3800+ CPU 939 pin, 4 gigs of DDR ram. The 2 hard drives are 250 gig SATA WD. Tried 2 old power supplies, different brands, that tested about the same. New power supply is a Corsair VX450W.
Here’s the numbers from the tests I ran.
Old power supply about 50% efficiency:
- Motherboard booting Linux off of a flash drive – 0.64 amps.
- With 2 hard drives – 0.85 amps
- With Cool and Quiet off – 1.01 amps
- Cool and Quiet On or Off – running DOS – 2 hard drives – old power supply – 1.47 amps
New 80%+ efficient power supply:
- Motherboard booting Linux off of a flash drive – 0.39 amps.
- With 2 hard drives – 0.52 amps
- With Cool and Quiet off – 0.62 amps
- Cool and Quiet On or Off – running DOS – 2 hard drives – new power supply – 0.92 amps
Cool and Quiet running DOS (OS doesn’t understand power savings)
- Cool and Quiet On – running DOS – 2 hard drives – new power supply – 0.92 amps
- Cool and Quiet On – running LINUX 2.6.24 – 2 hard drives – new power supply – 0.52 amps
- Cool and Quiet Off – running DOS – 2 hard drives – new power supply – 0.92 amps
- Cool and Quiet Off – running LINUX 2.6.24 – 2 hard drives – new power supply – 0.62 amps
Conclusions based on the numbers.
The “old” power supplies were not old like something from a 1980s computer. These were actually modern 24 pin power supplies bought recently. The decrease in power usage based on the power supply is 39% across the board no matter what the load levels are. Based on knowing that the new power supply is 80%-85% efficient we can calculate the old power supplies to be 50%-53% efficient.
Cool and Quiet at idle saves 16%.
In order to take advantage of power savings you need an operating system that understands how to save power. When running DOS the cool and quiet setting had no effect. When running Linux however with Cool and Quiet off there was a 33% power saving at idle. And with cool and quiet on the savings increased to 43%. It is likely that old Linux and BSD kernels would be like running DOS.
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New power supply and cool and quiet at idle – 49% total power savings at idle! Comparing all 3 factors including Linux vs. DOS, at idle we drop the power usage at idle by 65%. And if you replace the 2 hard drives with flash the power usage goes down by 78%.
I haven’t yet replaced all my power supplies but I am now running 7 computers.6 of them have dual core processors and the 7th has a quad core. Most have 2 hard drives, one has 3 and one has 4. With the 7 computers I’m down to less that 12 amps and when I replace the power supplies in 5 more computers I expect to get down to around 8-9 amps. I may be able to add 2, maybe 3 more computers in the future and stay under my 15 amp limit
By using these techniques I will be able to power 9-10 computers instead of being limited to 6. This is a huge increase in efficiency.
So if you want to save power, do these 3 things:
- Replace the power supply with an 80%+ efficiency power supply
- Turn on Cool and Quiet (AMD) or Speed step (Intel) in your BIOS
- Upgrade your computer OS to a modern operating system
Most people don’t know this but computer data center, where the Internet lives, uses huge amounts of power running millions of computers 24/7. If there’s anything to be learned from this to make the world greener law makers should pass regulations requiring manufacturers to use one 80%+ efficient certified power supplies on electronic device or give tax incentives for doing it. The technology is there to do this and even if it costs slightly more to build it will pay for itself in power savings. Call your congressperson about high efficiency power supplies.
Follow Up.
I have now replaced the power supplies in all 7 of my computers. Instead of pulling 12-14 amps at peak times I’m now pulling 7.5-9 amps. That’s a little better than 1/3 power reduction.
You may want to check on the 15 amps HE is providing. If it truly is a 15amp circuit then the breaker is meant to run at around 80% of that 15 amps on normal load. If you run above the 80% threshold for long periods of time you end up running the breaker hot and it dies out sooner and is more prone to tripping before the 15 amp limit. NEC requires that all circuits basically be designed at around an 80% max average usage.
D~
“current total demand from data centers in the PG&E region is 400 to 500 megawatts at any given moment. That has increased by between 50 and 75 megawatts in just the past 18 months”
Folks don’t realize how dramatically this expansion is happening. All the empty capacity from the dotcom bust has been filled. Our sucking economy isn’t going to make a difference other than rate of expansion.
http://tinyurl.com/2572lq
Terrific post, Marc.
You could also make your life easy and consolidate all 10 physical servers into a single, powerful VMware ESX host with dual sockets, 8 cores and 32GB ram. Something like a Dell 2950 loaded with 10KSAS drives will consume 5A at boot, 3A running.
What I find amusing is that HIGH efficentcy Power supplies have been around along time. But, only NOW have the prices FALLEN, to reasonable prices.
This is fun, as ALSO, machine FANS have come into use, and THEY have been cheap along time. Some of THOSE CHEAP computer fans, REALLY SUCK(badly).
Iv seen fans that can only move 35sfpm air and cost a Small fortune, when a Good $5 machine fan that can move 80+sfpm MAY sound alittle loud.
Iv only seen 1 Case I liked for Air flow. And my NEXT case I WILL MOD with Vents on the TOP, and ALL fans Pulling INTO the machine and OUT the top.(Im about ready to get a 12″ fan and put it on the CASE SIDE, using nylon as a FILTER).
Also, I would and WILL, Lower my DVD/CD down 1 or 2 slots, to give it MORE ROOM..
For those in the know… Have you noticed that 80% of MOST hardware problems come from HEAT??
Laptop to DESKTOP…that is the killer.
#4’s suggestion of vmware server is a good one.
Rule-of-thumb, limit the number of virtual servers to the number of physical Cores of the server, minus one, for decent performance.
Thus a 4 cpu quad-core, 16 cores, will power 15 virtual servers at about 80% capacity of each of the cores. Thus a core running at 3.2Ghz will seem like a 2.8Ghz inside the virtual.
With advanced settings, a single virtual server can have a MAX of two cores.
So if you need the power of a quad core, for running the GUI + Database, going virtual will seriously slow things down, be warned.
Also, each virtual cannot read & write on the same HD slice / partition. Just as if you had physical separate machines.
I’ve seen many “large” database-driven web applications go the virtual route, then get swamped with telephone calls about poor performance.
Instead of 80%, pretend it’s 50%. Especial HD access. Imagine 8 virtual machines talking to the same SCSI bus, at the same time.
Slooooooooow
“When buying and selling are controlled by legislation, the first things to be bought and sold are legislators.” — P. J. O’Rourke
Better than a law requiring computer makers using the more efficient power supplies, require the gov’t computers use them. The increased production will bring down the cost of the PPS.
I’m going to have to get one of those meters. I ran a power strip for two years with a steady load and melted the ON/OFF switch. By good fortune, it failed “open”. Better to plan than to rely on luck.
BTW, I’ve been hearing nasty things about those varistor surge suppressors, like they sometimes catch fire. Has anyone heard anything on them?
…or turn them off.
Actually I’m using OpenVZ virtualization. I could have gone on about that but wanted to keep the article reasonable in length.
I second the notion that HEAT is a killer on everything within the computer. I mod my computer to put a washaable electrostatic fliter on the right side of my box with a silent 120MM fan pulling air thru it to give my box positive pressure and completely clean air-no bunnies in the box.
Totally oversized for the box “BUT” filers the air in my room as well. Once a month I release the filer and run the hose over it and let dry.
Everything is healthy, clean, and efficient.
Now, if you’d’ve used PC’s based on Via miniITX you’d be saving a heck of a lot more. Did you really need those dual core processors? I use a Via miniITX daily and they’re plenty powerful, long as you don’t plan playing the latest FPS game or running AutoCAD. What’s more they’re very robust and tolerate 24/7 very well. Oh and did I mention they cost ALOT less? Most people don’t realize just how much overkill there is in PC processor power these days.
#12, Good mod, bobbo. My VAIO tower has the drives in a completely separate module on the top of the tower with its own fans and filter, the new 80% pwr supply and var. speed fans throughout, works great with ASUS bios.
Did you see this new breakthrough in fans? Talk about efficiency, from the NSF,
http://tinyurl.com/ywv7ss
#14–Bubba==thanks. Yes, one of the easiest and most satisfying mods around==I need to clean up my desk and take a few pictures of it. Just imagine the flat right side of your case==put a picture frame of 3/4 inch square pine wood around the edge and just mount your flat air filter over that. Only need to cut a hole in that right cover to allow airflow into the case. Mount fan where it will pull air. Whole thing adds 1.5 inches of width to the machine. The light on the fan is visible thru the filter==when I can’t see it real well, time to wash the filter.
Yes==I did see that new cooler technology. I figure I can use it in 10 years? Things need to get real cheap before I can play with it. I normally buy two of any new tech. One to use as instructed, the other to play with until I break it.
Contra–I kinda like “old technology” that you can just look at and see how it works? Work vs Hobby kind of thing.
#14–Bubba==forgot to say==I did the same thing but in the bottom of my case. (I actually built a 8x8x24 inch plywood box for my midtower to sit on) Also added a second separate power supply to run 6 extra hard drives, fan, and lights for all the video recording I do==all within that box. Drives are also connected thru esata==so I have normal operation with 4 drives in top case and then “video days” with the other 6 drives going in the bottom==all by throwing one switch and connecting one cable.
#16, bobbo, sounds way cool. you could easily write a quick article with several pix and post at the cage match, link to it from here. I would like to see the mods and your tower.
#17–I agree==I feel guilty everytime I mention my mods and don’t have a slide show to go with it. Somewhat–got out of habit of using my camera and even now having to relearn the commands and find the bad battery out of four==but kinda also, everything I do is spit, bubblegum, and duct tape==not pretty, just cheap and easy.
I wouldn’t want my abortion of materials and “close enough” attitude to put people off doing their own mods.
wait a sec. Socket 939 systems can’t use DDR2 ram, only old DDR ram, or am I missing something here?
I’m thinking competitive hamsters in running cages linked to an AC generator. Shouldn’t take more than 1,000 hamsters. It’s not clean, efficient or cheap, but it might be fun to determine the hamster count required to power the servers. As a baseline, hire a go-fer and rig an exercise bike to an AC generator and measure their oxygen and caloric intake to see which is more efficient hamsters or humans. My bet’s with the hamsters.
Move to Canada and run the computers with the 50% Eff. Psp. in the winter. You will be able to run the furnace less because you are using the computer electricity twice. The opportunity to have your cake and eating it to does come around very often. Then on the other hand the summers could be pretty ruff.
Hey, now that was a useful and interesting post, Mr. Perkel! Kudos to you. I’ll look into buying one of those gizmos.
That Kill-A-Watt thing is cool, I ordered one. You know, in Switzerland an IBM-built center erected for GIB-Services AG is using its excess heat to warm a local swimming pool.
#11- You nailed it. The reason things get mandated is because they cost a lot more – therefore people have no real motivation. If it costs a fortune up front to save amount of energy that doesn’t recoup the initial cost in reasonable time, why bother?
You want people to do something, find a way for them to do it that saves them money. They’ll do it.
#24–IGW==right you are, and the very best argument for putting a one dollar carbon tax on gasoline. sliding scale to add a dollar a year. Lets let the market figure out the best alternative.
Good advice, well stated.
Not only will VMWare make better use of the power, and reduce the heat, it makes better use of the resources your system has available (disk space, RAM, CPU time, etc)
I corrected the DDR2 error and also suggested a tax credit for 80% power supplies.
Power factor is possibly a reason that 15 A could not supply all of those machines. The power factor is related to the difference between the “real” power that is actually being consumed and the “apparent” power which is the total (volts times amps) that is moving through the wiring, although I guess that some really high-end machines might be running at over 200 watts each. Most of what I have ever seen is <150 watts, and since these are servers (I assume they don’t have the big fancy space-heater graphics cards)
A device with a low power factor will be sending lots of current back and forth through the wire, but will actually be demanding very little power. The capacitors and inductors in the device acts as “reservoirs” which are both taking power from the grid and sending it back into the grid, so the current is quite high but actual energy consumption is lower (these back-and-forth oscillations are simply current moving around without consuming energy)
Improving the power factor is a good thing, since it means that wiring does not have to be so thick to handle the excess current, there is less compensation (other capacitors and inductors) installed by the utility company, and less energy is wasted in the wiring (since heat loss in wiring increases with the square of the current)
I think that the wattmeter will measure real power in watts. Get that number, divide by 120, then divide that number by the amperage that was measured, mult. by 100, and that will be the % power factor of the whole setup. 100% is best. A lot of old power supplies are in the 60% range, I have seen as low as 30% on some devices (e.g. cheap inkjet printers that have both wattage and amperage ratings on them. PF can easily be found with both of those numbers)
But circuit breakers and wiring only care about amperage, so that is what needs to be reduced. Any energy savings are also very good as well.
I guess the amps are given under a 110 V voltage, but that would be nice to give the consumption directly in watts 🙂