[mythtv-users] Any advice on cooling down my backend

Edmund edmund.1 at dial.pipex.com
Sun Oct 5 18:42:33 UTC 2008

Thank you everyone for your help a while back. I have now followed 
through with a few ideas and
I thought I'd post my results.
>> Do you have cool and quiet running? Activate the ondemand governor so
>> the system runs at 1GHz most of the time. This will save 20W+
Thanks, I do now.

> Also, depending on the number of disks you have in the backend you can save a fair bit setting spindown times using hdparm.
I have some numbers. In each case the numbers are averaged over whole 
periods of 24 hours as I have very variable usage. These numbers are a 
little higher than I ultimately expect as I have been messing around 
during the day writing scripts and so the discs have been spinning down 
less than I would hope. In all cases when I use hdparm I use -S 120 or 
10 minutes.

Six discs (no DVD) no hdparm      199W
Six discs (no DVD) hdparm            191W but 4 disc are in a software 
Raid 5
so remove raid 5                           167 W
turn on AMD cool/quiet                  137W
remove the only graphics card         121W

These are not scientific there would have been different loads each day 
depending upon the programmes being recorded, but that is roughly quite 
a lot during prime time and then very little the rest of the day, no 
transcoding, all recording is DVB-T, though when I first removed raid 5 
there was quite a lot of disc copying going on.

The motherboard is a consumer Asus board, but there is a setting to 
ignore all error on boot and with this set it does boot with no graphics 
card. (Without it set it doesn't.)

> The only real downsides are that it takes a few (up to 30) seconds
> to spin them back up which can make for noticable lag times when
> using a frontend and you may want to add a minute pre-roll for recordings.
> On my backend with 7 disks in two software raid 5s plus a system disk
> using a kill-a-watt style reader:
> ~215W reading from all drives... (using dd, so cpu mostly idle)
> ~130W with all drives spun down (`hdparm -y`)
> ~185W with drives spun down and CPU at 100%
> ~240W with all drives reading and CPU 100%
> cheers,
> Owen.
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