Drobo

Heat comparison 7200 vs 5900rpm

My Drobo v2 is filled with 4 2TB Hitachi 7200rpm. When I changed out a drive from a 1.5TB a few weeks ago, I was hearing the fan running most of the time during the 72+ process of relayout and I started giving it more thought.
Although the room with the Drobo isn’t very hot, I have, in general, noticed that the fans run off and on with this Drobo, and I have thought maybe the fan shouldn’t run so much but wasn’t super concerned. During a re-layout, the drives run for 3 days or more ( I have 3.5TB of data on the Drobo). This turned out to be a good opportunity to identify how hot the drives are getting. So, being aware of the some of the suggestions here that 5400/5900 rpm drives perform equally as well in the Drobo, i thought about changing out to a lower rpm drive in order to see the effects.
Big difference so far in observed heat. I replaced the bottom 2TB 7200rpm with a 2TB 5900rpm. The relayout is going on for 48 hours so far. The 7200rpm ares burning up. I can only keep my hand against any of them for a few seconds.
But, the 5900rpm is very warm but I could keep my hand against it comfortably.

If there is truly no advantage to 7200rpm versus 5900rpm in the Drobo v2, due to CPU design, then I am strongly considering changing out the lot and re-using the 7200rpm somewhere else.

What speed drives do you have?

i’ve only ever used 5400rpm

there is no difference in normal drobos, apparently even in the drobopro although the difference is measureable but is very marginal and you probably wouldnt see it in real world useage. only the drobo elite really benefit from fast drives.

of course its not just a matter of relative speed or even heat, but dont forget the reason that the 7200 rpm drives run hot is because they draw more power, and that means they cost more to run too! (its not a huge amount - but since a lot of people keep their drobos on almost all the time, with 4/5/8 drives running pretty much 24/7 the costs do add up!)

I have 7200RPM drives in Drobo but only because that’s what I had on hand. If I replace them I’ll go with slower (and cheaper and cooler) drives.

I have WD GP in my four slot QNAP and those are variable speed. I have Seagate 5900RPM drives in the new eight slot QNAP. In both cases I’m happy with the performance and the chassis is fairly quiet since there’s not as much heat to dissipate.

The changeout has about 6 hours left to go; the bottom drive is still warm, while the upper 7200 drives are hot. I am definitely going to change these as I can.

“I have WD GP in my four slot QNAP and those are variable speed.”

Argh - my pet peeve!

no no no no no

they are not variable speed

they ALL spin at a CONSTANT speed

the confusion was because when they first came on the market WD issued a press release giving a range of speeds, saying something like they used different speeds to optimise performance or something

after a minor uproar they had to issue a correction pointing out that they meant each model’s speed may vary when compared to other models but each drive would use a single FIXED speed

the design of the motors which hard disks use makes it nigh on impossible to vary their speed

plus… if you think about it - the head is flying over 1s and 0s, if it read “1” for 3ms… it knows how many 1’s that is if it knows the speed its going at… if the speed is varying it becomes ridiculously complicated to work out how many 1s it measured.

and… if it were easy to change speed - even say between two fixed speeds, dont you think all laptop hard disks would run at 5400 on batteries and 7200 on mains power? they cant even get a hard disk to switch between two constant fixed speeds.

AND the fact that EVERY SINGLE ONE of the WD’s spins at 5400 (so far) has been confirmed by very very geeky people who hook up a CRO to a microphone and actually measure the “hum” of the drive - if you know the frequency of the hum, you can work out the rotational speed of the disk making it. and as yet, not a single WD GP model has been issued at anything other than 5400.

when they first started selling them - since they never said the actual speed - a lot of websites filed them under “7200rpm” on their online shops (just because that pushed the price up), and because their continuous read performance wasnt too far off 7200rpm drives at the time, since the GP range had very high areal densities.

That’s what I get for believing my disk vendor’s description of rotational speed (they still list it as “variable”). :slight_smile: My other vendor lists them as spinning at 7200RPM.

The WD product spec sheet for the WD15EADS doesn’t make it any clearer though listing “Intellipower” under rotational speed (http://www.wdc.com/wdproducts/library/SpecSheet/ENG/2879-701229.pdf). They then go on to define Intellipower as: “A fine-tuned balance of spin speed, transfer rate, and caching algorithms designed to deliver both significant power savings and solid performance.” This, to me, reads like it can vary the spin speed to affect the transfer rate depending on the caching algorithm. Marketing, two drink minimum.

ooh their description just says a fine tuned balance - it never says that it can vary, its “tunes” at the point of manufacture,and then stays like that until the day the drive dies.

and yeah - see my previous comment for vendors shoving them under 7200rpm , since WDC dont officially say otherwise[hr]
and just for clarity - what they actually mean by balance, is that when the arm is moving the head to seek, it takes account of how fast the disk is going, normally the arm would just snap into place, and would sometimes then be waiting for th eright part of the disk to rotate and be underneath it. the Gp drives work out how long the arm has to get to the position it needs to be before th bit of disk it needs arrive there, then only moves the arm at the speed needed, this can dramatically reduce heat and power needed and obviously since the arm isnt thrashing quite as much , noise.

(it still does move very fast, but it could be as twice as slow as on a regular disk)

Well “a fine tuned balance” really doesn’t say anything. It’s like those descriptions of wine that say “presents a fine tuned balance of kumquat and avocado flavors with chocolate overtones”. Really? :wink:

exactly, so i wouldnt read into that that the speed is variable :stuck_out_tongue:

I previously had Hitachi 7200 drives in my FS but swapped them last week with the Seagate LP drives. I did it because my workstation drives crashed and figured the Seagate LP would be a better fit for my Drobo.

I had already changed the fan in my FS to a silent fan, so these drives would be quieter and cooler. After swapping out the drives, I measured the drive temps and found that the LP’s are running about 10 degree F cooler than the Hitachi 7200. I haven’t noticed any difference in performance at all and they are definitely quieter.

at last! a review with a clear explanation:

http://www.anandtech.com/show/3981/western-digital-caviar-green-3tb-and-my-book-essential-3tb-drives-reviewed

"I asked WD for more specifics and I got a reasonable explanation. In the Green line WD optimizes for power consumption. It attempts to make all drives consume roughly the same amount of max power, which happens to be 3 - 5W below a typical 7200RPM drive. The spindle speed isn’t dynamic, it’s set at manufacturing and remains at that.

All green drives will spin below 6000 RPM and the spec never drops below 5400RPM. What this means is that all 2.5TB drives will spin at one speed while all 3TB drives may spin at another, both between that 5400 RPM to 6000 RPM range."