How long does it take a hard drive to STOP spinning?

[MitzEclipse]

Hi All,

I was wondering if someone could help me find a white paper or some type of documentation that states how long it takes a the average 7200RPM and a 5400RPM Hard drive to completely stop spinning.

I'm not sure if there is a difference between brands (ie: how long it takes a Maxtor and a Western Digital hd to stop spinning) but I'd just like to learn more about it.

Thanks all.

 

[techfuzz]

I had a good laugh when I read the title of this thread. Whew... I've never seen a whitepaper on the subject, but of course I'll offer some facts on the issue.

The time it takes for a drive to stop spinning would be dependent on its acceleration constant. The acceleration constant relies on the friction coefficient. The friction coefficient for each drive will differ because of the weight of the drive platters and type of bearings used. Additional factors like atmospheric pressure and humidity have a extremely minor effect on the whole process as well.

I'm sure if you happened to gather all these numbers together, someone here can produce the appropriate equation for you.

techfuzz

 

[MitzEclipse]

Hm.. can anyone give me an estimated time it takes for the 'average' hard drive to stop spinnion? 30 seconds? 1 min? Thanks

 

[LiekOMG]

About 10 seconds i'd guess. Shouldn't need longer than that to stop.

 

[MitzEclipse]

Aren't the disks in an almost frictionless environment within the harddrive's case?

 

[mechBgon]

IIRC, the datasheet for my old Quantum Atlas 10k said 17 seconds to spin down completely. (edit: that is a 10000rpm drive, however)

 

[everman]

Why exactly do you want/need to know? If you want some more fun calculations try figuring out how long it takes a specific drive to read a cluster,track,sector. Make sure you take into account all variables. I had that on an exam last week, not too hard

 

[MitzEclipse]

Well, if you guys really want to know why I want to know how long the hd takes to stop spinning.. it's because I am doing some timings on various computers. Can't really tell you why , but what I am doing is putting the computer in standby and hibernate and timing their speeds. I want to know how long I should wait until I should power up the computer. I don't want a spinning hard drive interfere with my timings.

Does anyone have any hard facts on how long it takes to stop spinning the HD?

 

[MitzEclipse]

Originally posted by: mechBgon
IIRC, the datasheet for my old Quantum Atlas 10k said 17 seconds to spin down completely. (edit: that is a 10000rpm drive, however)

mechBgon, do you by chance have that datasheet of your quantum atlas? If I could find some data like that, I would really like to obtain it.

Thanks!

 

[Alphazero]

Wild guess here.

You stop hearing the noise after 2-3 seconds at most. After that it could take around 5-10 seconds to come to a complete halt, since the manufacturers would make the platters with the least possible friction.

 

[dkozloski]

Because most drives have permanent magnet motors there will be some dynamic braking effect as opposed to a frictionless spindown. The weight of the platters and the distribution of mass will have a great affect on total inertia. Some platters are aluminum and some are glass. This is one of those questions where there are so many variables that you can get any answer you are looking for. As far as determining when rotation has stopped, if you hold the spinning drive in your hand you can feel noticable gyscopic forces that diminish as the drive slows. this might be of some help. It's kind of like the question of does the light really go out in the refridgerator when you close the door.

 

[Ilmater]

I'm convinced mine never goes off. How else could the refrigerator just "know" when I'm about to open it? I've tried tricking it before; you know, by standing there, turning my back to it and then spinning around real fast and trying to catch it unawares with the light off. It never works. Dammed thing is smart (sic).

Oh, I know that it stops within 20 seconds, but that's it.

 

[dkozloski]

I spilled chocolate syrup on the switch on my fridge and that slowed it enough that I could catch it with about 0.4 seconds to spare.

 

[Intelman07]

I listen to my hard drive (or i did once) and it took bout 6 sec for a WD800JB to stop. Must have a brake or something but the noise completely stopped after 6 sec