Re: Use of WD20EARS with MDADM

[Simon Matthews <simon.d.matthews@gmail.com>]

On Thu, Apr 22, 2010 at 9:13 AM, Khelben Blackstaff
<eye.of.the.8eholder@gmail.com> wrote:
>> I believe that these disks only come in the "green" variety.  I recently
>> picked up a 1.5 tb version for testing and cheap bulk storage, and I
>> would not suggest using them in a raid array because the green drives
>> firmware automatically parks the head after 8 seconds of inactivity and
>> reduces the rpm of the disk.  The constant parking can quickly wear out
>> the head under high use and there is no way to disable this "feature".
>
> As previously mentioned wdidle utility can disable the head unloading.
>
>> The specifications say it's good for 300,000 cycles, so do the
>> math... getting 5 unloads per minute would lead to probable failure
>> after 41 days.  Granted that is about worst case, but still something to
>> watch out for.  In order to make it the entire 3 year warranty period,
>> you need to stay under 11.4 unloads per hour.  If you have very little
>> IO activity, or VERY MUCH, then this is entirely possible, but more
>> moderate loads in the middle have been observed to cause hundreds of
>> unloads per hour.
>
> WD mentions in the customer help (Answer ID 5357) that these newer drives
> were validated to 1M load/unload cycles and not 300K.
>
>>
>> If you want to fix it, then wdidle3.exe worked for me.  Search for:
>>
>> wdidle3_1_00.zip
>>

I just looked at a WD green drive that was in a RAID1 set for several
months. The drive is an older model -- WD10EADS, but I think similar.
I did not use the widdle utility and the S.M.A.R.T. data reports a
load cycle count of 42. The RAID set held user directories, so it was
either under constant access (daytime) or not at all (nighttime, apart
from during backups).

Simon
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