[mythtv-users] raid array spin down possible?

Raymond Wagner raymond at wagnerrp.com
Mon Sep 26 23:40:38 UTC 2011

On 9/26/2011 18:38, Neil Cooper wrote:
> --- On Mon, 9/26/11, Raymond Wagner<raymond at wagnerrp.com>  wrote:
>> From: Raymond Wagner<raymond at wagnerrp.com>
>> Subject: Re: [mythtv-users] raid array spin down possible?
>> To: "Discussion about MythTV"<mythtv-users at mythtv.org>
>> Date: Monday, September 26, 2011, 11:40 AM
>> On 9/26/2011 14:31, Neil Cooper
>> wrote:
>>> My backend has a single 1TB HDD (for booting/OS and
>> recorded TV shows) and also 3 HDDs in a raid array for saved
>> shows, other media and general NAS. The array is a Linux
>> "software" type (i.e. mdadm --create) raid 5. All drives are
>> SATA. It's running "standard" Ubuntu 64 11.04 (not
>> mythbuntu).
>>> Both because the raid array is hardly ever in use and
>> because the box gets very hot with all drives running, I
>> would like to spin down (just) the raid array whenever
>> possible.
>> A 7200RPM drive is going to use about 8W each, spun
>> up.  While spinning
>> them down to save that 24W is a nice idea, if that little
>> bit of
>> consumption causes you thermal problems, you really have
>> more important
>> issues to deal with than saving a bit of electricity. 
>> Are you even
>> running a fan in that case?
> I really would appreciate some tips on my actual question of how to get my drives to spin-down, as I'm sure getting it working would make a real and practical difference to my heat issue.

No, it won't.  Considering all the drives are part of a single array, 
used to store media content, you can expect them all to be spun up for 
several hours at a time as you are watching movies and other content.  
At a bare minimum, your thermal design should be capable of handling 
those drives long enough to handle 2-3 movies.  As mentioned, reduced 
power consumption from spinning down drives is nice, but is a completely 
independent issue from your thermal problems.

Make sure your array is mounted with 'noatime', so Linux is not trying 
to update metadata for those files.  Check if smartd is polling those 
drives and disable it.

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