Re: Green drives and RAID arrays with partity

[Stan Hoeppner <stan@hardwarefreak.com>]

On 9/25/2011 6:02 AM, Marcin M. Jessa wrote:
> Hi guys.
>
> I was wondering if it's safe to use so called green drives in RAID 5 or
> RAID 6 with md?
> Drive such as Seagate Barracuda® Green 2TB ST2000DL003 or Western
> Digital Caviar® Green™ 2TB WD20EARX have TLER off and reading misc
> forums I understand that it would be a good idea to buy drives with that
> option available.
> On the other hand some people claim that Linux/Solaris/BSD based
> software RAID may be able to work just fine with these drives.

That won't make a lick of difference if you attach them to a crappy 
HBA/RAID card or mobo down chip, and/or with a buggy driver, or plug 
them into a crappy backplane.  Note the recent discussion of the 
SuperMicro/Marvell HBA, mvsas driver problems.

When you have a problem such as yours, and you ask for help on this, or 
any other Linux kernel list, it's a really good idea to post all of the 
relevant information up front.  Why?  Because most often when drives 
drop out of arrays it is not because a disk failed or the disk has buggy 
firmware.  It's most often because of problems elsewhere in the storage 
stack, either hardware or software.

Crappy HBAs and/or drivers, loose or dislodged cable connectors, and 
crappy active/passive backplanes are the primary movers when it comes to 
good drives dropping out of arrays.

That said, assuming you have a good SAS/SATA ASIC/driver combo and 
stable backplane, etc, I'd say buy the WD RE4 or Seagate Constellation 
ES as they have 5 year warranties, TLER, all the good stuff for RAID 
use.  Which is why they are sold as "enterprise" drives and cost more 
than consumer cheapos like the various Green "drives".  Both the RE4 2TB 
and Constellation ES 2TB are $200 each at Newegg.  Unless you actually 
*need* that much total space, I'd go with the 1TB models, paying ~half 
the cost of the 2TB drives.  The 1TB Constellation ES is $110.  So with 
5 drives you'll save almost $500 on drives, with 4TB usable space with 
RAID5.

Again, I implore you to investigate all other portions of your storage 
stack before blowing money on drives, which may not be the cause of your 
problem.

-- 
Stan


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