player-x

WD RED spinning at different speeds.

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Is it (in)correct that all the WD REDs are spinning at different speeds, from the factory or dynamic, to cancel out harmonic vibration.

I ask it because i read different information about it.

Edited by player-x

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No hard drive actually reads or writes as the spin speed varies. Drives can (and do) have different speeds in idle mode; it's quite frequent on laptop drives, for example. When heads are parked on the ramp, the drive often spins down to save power and only spins back up right before the heads are unparked.

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No what i understand from it, is that the REDs are programed from factory whit slightly different different RPM settings.

Something not that hard to do, as modern hard drives have similair PWM steering as case fans have, and they only have to program them to differ lets say in 5 rpm steps, then to stay between 5200 and 5300 rpm, you can have 20 different speed settings.

Chances to get lets say 8 with the same RPM settings is 20^8, even more then 2 with the same settings is gone be rare.

It would be a easy way to cancel out harmonic vibration.

And to program to dynamic change speeds would also not be that hard, as modern hard drives have motion sensors, if they can detect earthquakes that we cant detect our self's, they properly can also detect harmonic vibration in a array or assume there is harmonic vibration, and change speeds the moment the hard drive go's over a set vibration limit setting.

I read it in different reviews the mention of the option, i am just wondering if they using WD as there source or one and other.

As you people of SR are closer to WD then i am, i was wondering if you could ask them.

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So you're saying the drives can vary their spin speeds on the fly, while reading/writing or only when idling? If the latter, then sure, it's simple and common to do that. Hard drives have a trigger limit set to stop writing when detected vibration (either detected via servo or via sensors) so data isn't risked. If it's bad enough, it'll stop reading, too.

Changing speeds to cancel out vibration assumes you know what the target speed should be ahead of time. So it's conceivable that it's done at the factory, though having each drive set its own parameters sounds like a testing nightmare. But changing speeds during reading/writing? I don't see that happening.

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So you're saying the drives can vary their spin speeds on the fly

No, because i dont know, and was i wonder if what they ware saying in some of the reviews is true.

What i also are saying is that i dont think it would be that hard to make a table whit different speeds and different timings settings for those speeds.

Those different speeds could be set in the factory, but could also be set on the fly if triggered by the sensor.

Tho i believe its the first, if its used is more likely.

And wonder if SR could confirm it with WD?

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It's not hard to make the table. The difficulty is picking the correct speeds to avoid the resonances in question, as that can vary between drives. And if you test a large number of drives, you'll have variations, so it'd have to be something the drive would self-detect somehow (and that's way beyond my knowledge of drive FW).

Interesting idea, though.

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I think it will not be that hard to ship HHDs uselessly they come 20 in a box, and have all of those use different speeds, lets say in 5rpm steps.

And for now i think thats the most likely scenario they ship with different speeds.

The difficulty is picking the correct speeds to avoid the resonances in question, as that can vary between drives. And if you test a large number of drives, you'll have variations, so it'd have to be something the drive would self-detect somehow

Actually i think that would be not that hard, because tripping max resonances setting would happen on different moments depending ware the HDD is sitting in the array, the one's closer to the middle would be tripping the max resonances setting sooner then the one's closer to the more sturdy frame/case connection points.

Or use a scheme that would randomly pick rpm setting from the table at a given (sorta random) interval as long as the resonances setting is triggered.

And thus you would end up with different rpm settings for every drive, till you end the resonances problem.

/ontopic

Still wonder if SR could confirm it with WD?

Or dose the reviewers dont have that type of connections whit the hardware manufacturer's?

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This is a rather interesting topic, and I'm not sure if any hardware vendor does this. Can you point to some of the articles that you mention? I'd love to find out more.

Your concept of setting a random speed on boot is similar to how cron's RANDOM_DELAY variable works. In this case, when cron starts for the first time, it will set a random delay and base all tasks offset from that. This occurs at ever time it starts up and persists until it's stopped. You could easily imagine something similar for HDDs where they could pick a random offset on boot. This would be much better than hard-coded offsets.

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Can you point to some of the articles that you mention? I'd love to find out more.

The source is in Dutch, but i also red it on a German site, but cant find that one back that quick.

http://nl.hardware.info/reviews/5522/western-digital-red-6tb--red-pro-4tb-review-opslaggiganten

Om de levensduur in NAS’en te verhogen heeft Western Digital naar verluidt bijvoorbeeld een technologie ontwikkeld waardoor meerdere Red-schijven net op een verschillend toerental werken, zodat ze geen last van elkaars resonantie hebben.

-- Translation --

to increase lifespan in NAS systems Western Digital reportedly developed a technology that enables multiple Red discs work at a different speed, so they are not affected by each other's resonance.

-- Translation --

Every ware i read about, its little more then hints on the function, so i dont know what to think of it

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