Re: Use of WD20EARS with MDADM

[Bill Davidsen <davidsen@tmr.com>]

Stefan *St0fF* Huebner wrote:
> Am 25.03.2010 18:45, schrieb Asdo:
>   
>> David Lethe wrote:
>>     
>>> On Mar 25, 2010, at 11:20 AM, Andrew Dunn wrote:
>>>  
>>>       
>>>> Recently Dell is selling their WD20EARS (2TB) for 90$
>>>>
>>>> This being one of the best PPG (Price Per Gigabyte) snatches I have
>>>> seen, I was considering buying 8 of them for an mdadm array.
>>>>
>>>> Has anyone had experience with these drives?
>>>>
>>>> Note, they have 4K sectors.
>>>>
>>>> Thank you for your kind responses.
>>>> -- 
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>>>>     
>>>>         
>>> This is a low-cost consumer disk that is rated for a whole 2400 hours
>>> use in a year.  You get what you pay for. 
>>>       
>> I think the "I" in RAID stands for inexpensive :-P
>> Jokes apart, don't you think frequent scrubbing (e.g. weekly for a
>> raid-6 or 2/week for raid-1/10) is enough to compensate for this?
>> I would be way more concerned with ERC / TLER if it proves to be
>> nonsettable, but I might be wrong
>>     
>
> Just for those who like to read: ERC is a feature stated in the
> ATA-specifications, that's why the "quick hack" for smartctl was so
> easy.  But in the specs it is also noted, that the change a
> SCT-ERC-Command does will not survive a power cycle.
>
> So y'all will probably need some udev-triggered daemon, which runs upon
> connecting a disk, checking if this disk is conforming to the ata-spec,
> then finding out if it's part of a raid array.  If all answers yield
> "yes", it should call SCT-ERC with a configurable value, and probably
> some other "configure the drive"-commands (for tuning the idle timeout
> of wdXXears).
>
> I'll have to think about that as a project again ...
>   

I would think it was easier to just add a small section to rc.local, 
unless you antucipate lots of errors during boot and after udev gets going.

-- 
Bill Davidsen <davidsen@tmr.com>
  "We can't solve today's problems by using the same thinking we
   used in creating them." - Einstein