Re: Recommendations for RAID setup needed

[Michael Tokarev <mjt@tls.msk.ru>]

16.09.2015 18:53, Alex wrote:
[]
>>> All four are WD30EFRX-68EUZN0. They're not the cheapest WD disks, but
>>> they're also not the ones with the 5yr warranty. The last array I
>>> built using disks with 5yr warranty exceeded their capacity before the
>>> warranty expired.
>>
>> Umm, 1st google result showed this:
>> http://community.wd.com/t5/Desktop-Mobile-Drives/New-WD30EFRX-Red-Drive-Idle3-Timer-Set-to-8-Seconds-High-LCC-in/td-p/648821/page/5
> 
> I was really just looking for general input on RAID5 vs RAID6, but
> that is good information. I knew the drives weren't basic desktop
> drives and would be generally suitable for building a software RAID
> array.
> 
> Are you familiar with the idle3 time? It appears the idle3-tools can
> be used to disable the idle3 timer entirely, which would disable
> parking the head at all, correct?

An addition.  From hdparm(8) manpage:

       -J     Get/set the Western Digital (WD) Green Drive's  "idle3"  timeout
              value.   This  timeout  controls  how  often the drive parks its
              heads and enters a low power  consumption  state.   The  factory
              default  is  eight  (8) seconds, which is a very poor choice for
              use with Linux.  Leaving it at the default will result  in  hun‐
              dreds  of  thousands  of head load/unload cycles in a very short
              period of time.  The drive mechanism is only rated  for  300,000
              to  1,000,000  cycles, so leaving it at the default could result
              in premature failure, not to mention the performance  impact  of
              the drive often having to wake-up before doing routine I/O.

              WD  supply  a WDIDLE3.EXE DOS utility for tweaking this setting,
              and you should use that program instead of hdparm if at all pos‐
              sible.   The  reverse-engineered implementation in hdparm is not
              as complete as the original official  program,  even  though  it
              does  seem  to  work  on  at a least a few drives.  A full power
              cycle is required for any change  in  setting  to  take  effect,
              regardless of which program is used to tweak things.

              A setting of 30 seconds is recommended for Linux use.  Permitted
              values are from 8 to 12 seconds, and from 30 to 300  seconds  in
              30-second  increments.   Specify  a value of zero (0) to disable
              the WD idle3 timer completely (NOT RECOMMENDED!).

Thanks,

/mjt
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