[mythtv-users] Using spindown with SCSI RAID5?

[Steven Adeff]

On Thu, Jun 26, 2008 at 8:44 AM, George Mari
<george_mythusers at mari1938.org> wrote:
>> 2008/6/25 George Mari <george_mythusers at mari1938.org>:
>>
>>> Anyone out there had any success with spinning down SCSI disks in a
>>> software RAID5 array for power saving?
>>>
>>> I tried to spin down one of my 4 disks in a RAID5 array, using the command:
>>>
>>> sdparm --command=stop /dev/sdi
>>>
>>> This spun the drive down (good), but it also kicked it out of the array.
>>>  (bad)
>>>
>>> What I'm trying to do is just have it power down somehow after a certain
>>> time being idle, and then just spin up again when accessed without
>>> breaking the  but it seems that SCSI drives don't have all the power
>>> management options that PATA or SATA drives do.  (Or maybe just my
>>> particular SCSI drives don't have these features...)
>>>
>>> I'd love to hear from anyone with specific experience with trying to do
>>> this with SCSI drives - thanks.
>>> _______________________________________________
> Silvestro Roberto wrote:
>  > I think you can spin down only spare disks in the array!
>  >
>
> Well, I have read that the spare disks for a RAID5 or RAID6 can be spun
> down.
>
> But I have a small RAID0 array on my desktop made from 3 SATA laptop
> drives that I use for editing and transcoding home movies.  Through no
> intervention on my part, the drives spin down after not being used for a
> while, and whenever I access the filesystem on that array, there is a
> pause of maybe 2 seconds while the drives spin up, and then the array is
> just fine.
>
> So it seems like it could be done, but I'm just trying to figure out if
> only certain hardware supports the "spindown-without-breaking-the-array"
> feature, or if there is some way to do it I am not aware of.

I looked into this a while back when I was setting up my long term
storage RAID5 array. I believe it was possible, but in the end decided
not to do it (it gets used too often in my household). I believe you
have to disable all RAID monitoring, and make sure no running
processes will reactivate it periodically. I also played with
unmounting the array before putting it to sleep, which iirc worked
well, but was a pain to remount when needed.

-- 
Steve
Before you ask, read the FAQ!
http://www.mythtv.org/wiki/index.php/Frequently_Asked_Questions
then search the Wiki, and this list,
http://www.gossamer-threads.com/lists/mythtv/
Mailinglist etiquette -
http://www.mythtv.org/wiki/index.php/Mailing_List_etiquette