# power management for always-on home server

## greyspoke

Hi, I have been rummaging around here and other places for an answer to this, but probably don't know enough about it to know what to look for. 

I have been very pleased with installing Gentoo on my desktop machine, and have managed to deal with all issues by consulting the forums and the (excellent) Gentoo documents.  I now want to build a home server to keep backups on and store shared files (mainly music) for my Gentoo machine and three Windows machines belonging to other family members.   I am looking at a mini-ITX thing with 2 or three hard drives in it as a RAID array, to operate as a headless server with no GUI, just a very basic installation.  It will need to be available all/most of the time, but a slight delay in being available sometimes would not be a problem.

My question is, how to minimise power consumption with this, the thing will spend most of the time doing nothing?  All the stuff I have found out about sleeping and hibernating (I've read the Gentoo Power Management Guide) indicates a keypress or mouse movement is needed to wake the machine, or the sending of a magic packet over the LAN (which I don't want to get into).  Does this mean I am limited to spinning down the hard drives and slowing down the processor speed?  

Another answer I can't quite get to is whether there is any point in having the system (that is, stuff other than /home) on a separate HD from the data (eg on a solid state drive that will "spin up" quicker).  Once the thing is started up, will it need to read from the drive much or will it keep what it needs in RAM?

Any thoughts appreciated, thanks.

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## bobspencer123

well this is sort of off topic but have you looked into a sheevaplug or guruplug. I am getting one of these for essentially the same thing ... a headless server for home file sharing and to run my etree torrents with super low power consumption.

To answer your first question. I don't know a ton about power management but besides scaling down the processor and reducing consumption of the disc drives I don't see what else you could do with a server other then buy a "green" power supply that only uses the amount required.

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## snIP3r

hi!

i already use a home server with various  functions and i can agree bobspencer123's message. but i think it is more important so choose hardware with low power consumption (e.g. ion based motherboard with atom processor, hard drive with low power usage - e.g. samsung ecogreen f2 or f3 - and so on). for this hardware you then can use options to reduce power consumption (e.g. cpu frequency scaling using cpudyn). a good energy efficient psu is also recommended.

HTH

snIP3r

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## greyspoke

Thanks bob and snip, those plug things are cool, but look a bit more of a project than I was intending, though I am tempted.  Presumably the HD enclosure you plug into the plug (as it were) would need a separate power supply, so you would be looking at the total of the two vs a computer running off a single PSU.  

Anyhow, carefully selected bits for an Atom-based computer looks to be the way for me.

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## chris...

for low power consumption and adequate performance for sharing music files you could always use a real cheap laptop a usb hub and a bunch of usb sticks, that way you also have a terminal just in case and other features

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## matze_na

If you want to minimize power consumption and don't need an ION chip for video playback on that machine, which I think you don't according to what you wrote, consider going for an Atom with a netbook chipset.

Most Atom boards use a chipset with way too high power consumption considering it doesn't actually do anything most of the time.

I built a home server for similar purposes on an Intel D945GSEJT. This board comes with a (single-core, 32bit-only) Atom N270 with 1.60GHz and uses the same chipset built into many netbooks.

Power consumption with two 2.5" HDDs in RAID1 is somewhere between 15 and 20W, depending on current load.

An important factor are the hard drives, you should definitely go 2.5" since they use way less power.

In my case, I power the board with a PSU others use for TFT-monitors, 60W max. And the power for the hard drives comes from this PSU, too. It is grabbed from a connector on the board itself. If I connected a 3.5" HDD, the system probably wouldn't even boot because the (physically) bigger hard drives use waaaaay more power for spin-up and such.

Anything you do on a software basis to further reduce power consumption might yield some minor improvements, but selecting the right hardware is the single most important thing.

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