Drobo

Western Digital Don't Recommend End-User Drives in RAID or NAS???

While researching Western Digital Green HDs I came across this:
http://www.readynas.com/forum/viewtopic.php?f=24&t=32179

And more specifically:

[quote]…The unit is not recommended for NAS or RAID use, due to its end-user design. But, under normal use, rather than strenuous or highly demanding tasks, there should be not much issue with the unit.

Johnny T.

Western Digital Service and Support[/quote]

I didn’t find any information in the knowledge base.

I thought choosing hard drives would be a quick task. It never stops![hr]
This link suggests WD phone support say the same thing:
http://en.wikipedia.org/wiki/TLER#Western_Digital_Time_Limit_Error_Recovery_Utility_-_WDTLER.EXE

Hard Drive Manufacturers have standard desktop hard disks and enterprise/RAID level hard disks.

Ignoring performance considerations, the main difference between the two is that RAID level hard disks have TLER (Time Limited Error Recovery).

Basically it guarantees that the hard disk will respond to a query in a specified time even if there is a problem reading a block on the disk.

Standard Desktop type hard disks could lock up for a bit and take a while to respond - this often causes the RAID Array to kick out the hard disk as bad - even though it may just have a single bad block.

Drobo will kick out a hard disk if it has too many problems but in general people on this board don’t report a huge number of issues with the Drobo kicking out good disks.

The cynical would also say “of course they don’t recommend consumer drives when they can get much more cash for the enterprise level drives by spreading fear, uncertainty and doubt about their own products”.

In all seriousness, if you have lives or millions of dollars depending on your NAS/RAID system, then you SHOULD pay the extra for the enterprise-level drives. The typical Drobo isn’t in those situations, so I personally would have absolutely no qualms about using consumer-level drives in it. Also, all Drobos are using RAID-like setups for redundancy to guard against disk failures, not striping across disks for performance, so if one drive “dies” due to a situation like the one @ajspencer outlines, you didn’t lose the whole array like you would if you were in a RAID 0 configuration for pure access speed considerations.

Use the consumer drives. If one fails, you can always use a disk maintenance tool to check it out offline in another machine to see if you can save it for other uses after the issues are repaired.

The reason is that the new series available from WD disabled the possibility to modify the WD TLER setting. The Green/Blue/Black series have a TLER value too high for a RAID, resulting in the raid controler dropping the drive, thinking the drive is broken because his not responding.

From what I’ve understood, a RAID environnement control the drive error by himself. But the usual harddrive are made to search, control&fix the error by themself within a certain ammount of time ( that is defined by the TLER value ).

While the drive is fixing him self, the RAID drop it.

Before, a utility called WD TLER tool was giving you the possibility to change manually the TLER value. Now WD have made it impossible, and removed the tool from their site, while adding a new Raid Edition (RE) range of product. Honestly, they look like the exact same product, but with a TLER compatible with a RAID environnement, and twice the price.

By the way, the Green edition is only 5400 RPM. They don’t mention it anywhere, but I’ve received a RMA, and on the red sheet, the product was mention to be 5400.

Usually I don’t like to tell you what to buy, but clearly, don’t buy Western Digital if you think about raid.

But still, their is something I don’t quite understand, Drobo seem to come by default with WD Green drive, so maybe drobo is handling them differently from a regular RAID.

Yes its all up to the RAID controller on how it determines if a disk is bad or not. Data Robotics don’t publish details on how the internals of their Drobos work, but since its a consumer level device its designed to work with consumer hard disks.

Yup I know, and I agree that Drobo should handle that correctly, but as a customer, if I have the choice between anything and a WD for a close to RAID purpose, from what I’ve experienced, I’ll go with anything but WD.

That’s a poor decision since WD makes arguably the best performing consumer drives (caviar black and raptor) and lowest power consuming (green). WD consumer drives are not the only ones without TLER. It’s just that Seagate calls it Error Recovery Control (ERC) and Samsung and Hitachi call theirs Command Completion Time Limit (CCTL). I believe they only feature it in their enterprise drives as well.
Here are some references:
http://en.wikipedia.org/wiki/Time-Limited_Error_Recovery
http://www.hddoctor.net/what-is-error-recovery-control/
http://www.samsung.com/global/business/hdd/learningresource/whitepapers/learningresource_cctl.html

And an interesting discussion here:
http://forum.hddguru.com/samsung-cctl-seagate-erc-tler-t11630.html