why don't hard drives dynamically change rpm?

[draggoon01]

wouldn't it be useful if hard drives could spin up to 10,000 or down to 5400 depending on activity?

normally hard drives aren't under heavy reads/writes for long periods of time for most people

the benefits would be saving on heat and wear

 

[sniperruff]

i tihnk it would be expensive/difficult to do so

 

[Alex]

whoa thats such a good question !! i want to know the answer !!

anyone know?

 

[jjyiz28]

sniperruff answered it. its too expensive

did you know that for cd rom speeds up till i think, 12X, i did actually spin up when it was reading in inner circle, then slow down in outer circle, therefore the read rate would be the same. for 16x and up to 52x, the decided to just let it spin one speed, save on costs i believe. that 16x speed is only for the outer circle, therefore really, a 12x is actually faster than a 16x, and even a 24x i believe.

its all about cost. actually, spinning and slowwing down would cause more wear and tear rather than just one set speed.

 

[dkozloski]

Any time the disk was changing speed it would be inaccessible. This is the same problem that exists with drives in laptops in a power saving mode. Any time the drive is stopped or speeding up or slowing down it can't be accessed. As the rotational speed changes, the timing issues in clocking out and error checking data would get out of hand. Maybe some day, but I don't see it happening soon.

 

[Sunner]

I have a feeling this would cause quite a bit of strain on the motors as well.
Having to spin a disk up and down would be considderably harder on the motor than to just keep it spinning at 7200 RPM constantly.

 

[bendixG15]

What about CD_RWs ???

Don't they have a variable spin rate ????

 

[egale]

They may but their spin rates are no where near what a hard drive is. A 7200RPM drive turns 120/sec. A 10,000RPM drive would turn 167 times a second.

 

[sharkeeper]

There is no reason to make fixed disk technology CLV.

Cheers!

 

[Mark R]

They[CD-ROM drives] may but their spin rates are no where near what a hard drive is

The spindle speed of fast CD-ROM drives can considerably exceed 10,000 rpm when at maximum speed. Most CD-ROM/RW drives do vary the rotational speed depending on activity and which area of the disc is being accessed.

For optical drives there are different priorities - high speeds on an optical drive require large amounts of power, produce substantial vibration and noise and produce considerable amounts of heat in close proximity to fragile heat sensitive discs. It matters less than variable speeds hurt access time because access time is very slow anyway.

There would be little benefit in making an HDD that could vary its speed. Slowing the spin speed down would do little for noise and vibration and only slightly decrease heat (which isn't that big a problem anyway), while impairing access times.

 

[rjain]

CD-ROM drives can't be balanced perfectly so that keeping the drive spinning at the same speed requires minimal energy.

HDs are put together into one package, so the disk can be tuned to be very efficient at keeping its momentum.

 

[thorin]

1) As others have said cost (though I think it could likely be implemented in software/drivers...just like making drives spin down for power saving).
2) Also as others have said it would be extremely hard to continue reading/writting while the disk was rotating at a variable speed (ie: speeding up for load or slowing down for no load....at either extreme it would be fine).

Thorin

 

[Pariah]

It wouldn't make any sense to. There wouldn't be any benefits to implementing such a feature. Varying the spin rate would create considerably more strain on the drive motor than just letting it spin at one rate. Heat is pretty much a non-issue as well. When the drive is idling it doesn't create much heat, so spinning it down wouldn't do much of anything.

 

[spongebobfan]

I think the primary issue is air, the drives are made so that the head floats over the drive surface. If you change the speed dynamically, all of the physics engineering for the head float gets changed and too much can go wrong for a very little benefit...

Sponge

 

[Regs]

Hey, When solid state HDD's come around and at a affordable price, all our problems will be solved!

 

[rjain]

Originally posted by: spongebobfan
I think the primary issue is air, the drives are made so that the head floats over the drive surface. If you change the speed dynamically, all of the physics engineering for the head float gets changed and too much can go wrong for a very little benefit...

VERY good point. I think the drive head is kept parked until the platters are fully spun up for exactly this reason.

 

[piasabird]

When I had a IBM Hard Drive at one time they had some way to fine tune the speed. You could change the speed of the drive for better Harmonics.