What's the mechanical difference between 5400/7200 RPM?

And would it be possible to make a HDD that can switch between 5400/7200?

 

The question is weird. You don't have a choice, do you? So why bother ask?

 

It might be in the wrong section... Just asking if there's the possibility.
Edit: I changed "from" to "between"

 

The WD Caviar Green for desktops is a variable speed hdd. It's supposed to go from 5400 to 7200 depending on the load. There are criticisms of it though saying it's ineffective. I don't feel like searching for them now.

 

why would you want to? what would you hope to accomplish.

complexity breeds failure. keep it simple.

 

You could have it at 5400 when on battery and 7200 on mains power.

 

Although I haven't seen solid documentation regarding it, the WD Caviar Green drives are supposed to have variable spindle speeds. Problem is, often the initial latency is what counts for a snappy system, and if a HD spins down to a slower speed, this initial latency increases - defeating the purpose of the faster potential speed except in situations with extended file access/transfers.

Well, for one, 7200RPM drives generally provide better performance, 5400RPM drives generally provide better power efficiency. A variable spindle rate would therefore theoretically provide an effective hybrid between those two extremes.

 

hard drives already spin down and I am pretty sure that they already do this on their own to save power. there probably wouldn't be a point to this unless you're talking about having manual control over what speed it operates at. I guess that might come in handy if you want the ability to buy one drive and choose between speed and how much power it uses, rather than be stuck with whatever you got when you purchased it... I wonder if this can already be achieved by swapping or modding firmware in some manner?

 

You know what.. The power consumption difference will be around 0.1 Watts. You will not be able to observe any meaningful difference in battery life between 5400 and 7200.

Just check the white papers for both drives from various manifacturers.


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Spec sheets made by manufacturer isnt always accurate.

According to WD, both Scorpio blue and black use 2.5W of power but when NBR tested it using a multimeter the results were different.

 

I own 2 Caviar Green drives (1 TB AADS, 1.5TB EARS), they aren't noticeably slower than a 7200 rpm drive but they do run noticeably quieter and cooler.

 

WD's GP Intellipower drives actually run closer at 5400.

WD Green Power: A New Benchmark in HDD Acoustics & Power | silentpcreview.com

 

I mean in terms of copying, yes it is slower than my Caviar Black/Blue but only by a few MB/sec.

And I have it on a P35 chipset and an X58 chipset.

I mean sure benchmarks are one thing but actual "use", I hardly see a difference so for storage I will continue to use Caviar Greens.

 

That is a fairly ignorant assertion....

Component spec sheets often become a legally binging part of a purchase contract. Engineers and systems integrators depend on the accuracy of the info on those spec sheets.

Saying that a HDD spec sheet is inaccurate and then saying that NBRs infamous multi-meter readings are to be trusted as being more accurate is, well, damned silly.

NBR measures power draw at the wall plug where everything in the system is being measured. The inefficiencies of the external supply, the internal supply, changes in system draw as an OS changes over from one power mode to another, all of this and more get 'measured' the way NBR tries to do this.

Component spec sheets are done on a bench, with calibrated test rigs, and measure/document exactly how that component behaves.

 

Well there is always a discrepancy between lab testing and actual testing. We could apply this to alot of things, like car MPG. The sticker may say one thing but one could experience something totally different.

 

Even so there is still a big discrepancy on Scorpio Blue and Black even when put through the same test.

In this case, it didnt get measured at the wall plug. John Ratsey did it himself in an enclosure. I also remember Kevin built a testing jig which uses 2 multimeters to measure from the power rail but i think it was only used on recent reviews.

If i have the time, i would do it myself and tap into the power rail that feeds into the drive.

The figures also match up with Toms Hardware and storagereview results

 

did Ratsel use an adapter in the disk drive power cable (as close to the drive as possible, preferably using the manufacturing test connector available on the PCB) to provide connections for a lab-calibrated ammeter AND did he use a calibrated DC power supply to power the whole rig?

don't think so........

unless you test under those conditions with known-good equipment, then it's all guess work.

consider the meaning of an inaccurate drive spec sheet. Imagine for a second that a systems integrator has designed an 'enclosure' (or a huge disk array) that holds 1000, 2000, or 5000 drives. What would be the implications be for the power supply (both AC in and DC to the drives) of having a spec sheet that is inaccurate by 30/40/50% as consumer web blogs try to tell us they are.

 

Calibrated power supply? Guess work? You can just use a quality multimeter to probe the voltage and and amps being fed on the drives power rail. While it may not be industry grade testing, it is still very accurate.

 

Now you're just waving away engineering best practices with a 'who cares' to excuse shoddy work on other web sites.