Build an Energy Efficient Media Server

How much power does a home server suck out of the wall each year? My old media server used 80 watts. Last year I put together a silent MythTV Frontend (set-top box.) It only uses about 18 watts of power. What if a full fledged MythTV server were built on the same platform?

• How much power could be saved?
• Would the performance be acceptable?
• How much money would it save in energy bills?

Motivated by my fairly new Kill-a-Watt power meter, I set out to build the system to answer these questions and see if the results would be a system I would want to stick with.

Building the Box

Construction of the device is fairly straight-forward. I took my initial set-top box and started adding in, or should I say cramming in, more components to make it a fully functional media server. Components I added:

• Slim CD/DVD drive (laptop style)
• 160GB Hard Drive
• PVR-350 TV Tuner Card
• StreamZap USB Remote

The biggest construction problem was installing the PVR-350 PCI card. The case just isn’t designed for a full height card. The board was about 1/8” too wide for the horizontal slot. I ended up drilling a hole to widen the space for the PCI slot. Certainly not the most elegant solution, but it accomplished the goal. Cards like the PVR-150 may not have this problem, I don’t know. I was using the PVR-350 because I already had it. If starting from scratch, I would have gone with the PVR-150. The other case modification I needed to do was relocate a fan that the TV tuner was hitting up against. I re-attached it to a raised screw whole in a way that sucks air up from underneath the motherboard and hard disk directly into the exhaust flow of the second fan. I would think this should still keep things nice and cool.

I had a fully functional computer crammed into a set-top box sized case.

I used a StreamZap USB remote control (read my StreamZap Review), which was as easy as installing the batteries and plugging it into the USB port.

MythTV Linux Distribution

It needed an OS. KnoppMyth fit the bill this time, although I'm a MythDora fan as well. Check out my KnoppMyth Install Screencast to see the general process.

Power Savings

Prior to doing this, I hooked my existing MythTV server up to my Kill-a-Watt for about two weeks to get a baseline power measurement to compare against. Running on an eMachine T1842 (1.8GHz Celeron), the server consumed an average of about 83 watts of power. (It would jump as high as 130 watts when running a commercial detect job.) I suggest you get your own Kill-A-Watt and test your system. With only a little effort the Kill-A-Watt can help find enough power savings to more than pay for itself. Running roughly the same recording schedule and usage (I was able to migrate my MythTV recordings and schedule over,) the new system consumed an average of about 37 watts of power over the next three weeks. (Peaks at 41 watts during commercial detection.) So, what does that save? The roughly 45 watt power savings adds up to about 400KWH over a year, which equates to $40 a year. For the cost of power, I used $0.10/KWH which is what I see used as the reference cost on compact fluorescent light bulb packaging. $40/year in power savings sounds nice, but how does it perform?

Performance

Of course, these savings do not come free. Ignoring the hardware cost, the other major issue affected is performance. This is only a 600Mhz CPU on a motherboard better known for energy efficiency and size rather than performance – Is it up to the task? You certainly will notice the difference. You will mostly notice the performance hit in terms of sluggish UI response on a connected frontend. Not horrible, but noticeable. For what it’s worth, most of the time the response is still faster than the Digital Cable Set-Top Box supplied by Time Warner, my local cable provider. The worst problem is immediately after deleting a recording, the UI seems to lock for about 5-10 seconds.

Conclusion

Like many energy saving projects, there is some trade-off. But it’s still usable, and something that I think I’ll stay with for a while. It’s certainly a low end system in terms of performance, but it also uses less than half the power used by my previous system. For me, this feels good both from a money saving perspective as well as being better for the environment. If you are the type who will happily live with minor UI performance issues in exchange for saving energy, then this type of system is something certainly worth looking into.