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Old 3rd October, 2002, 12:32 PM
Aedan Aedan is offline
Chief Systems Administrator
 
Join Date: September 2001
Location: Europe
Posts: 13,075

Quote:
Originally posted by Winkie
One of the best ways to quieten hard drive noise is rubber washers
I'm avoiding rubber washers at the moment. I remember reading a Seagate whitepaper about such mounting methods and their effect on hard disks.

One of the assumptions made by the software is that the case of the hard disk will remain in the same position, regardless of the moments of force acting upon it. (from the HDD's point of view!)

When the drive comes to make a seek, it starts the heads moving towards the track wanted. Depending on the distance, the acceleration may be quite high. During the acceleration phase, the case experiences the effects of the change of momentum. This causes the heads to accelerate slightly more slowly than normal. As the software is basing the inital seek on a computation of where it is, where it needs to be, the weight of the heads and various other factors (Yes, it's making a guesstimate of how far/fast to move the heads!), the software's model now no longer corrisponds to the real world.

Exactly the same thing happens when the drive deaccelerates the heads towards the end of the seek. The case once again moves slightly, leaving the software's model out of line with the real world.

Of course, once the software realises that over the wrong track, it repeats the seek. As the seek is now just a few tracks, there's very little movement, so little effect upon the case.

On the other hand, the drive has had to make multiple seeks in order to find a track that would ordinarily only take a single seek. The result is that the access time of the drive goes up.

Yes, Seagate did test it in practice as well as in theory. I can't remember how much seek time went up, but it did go up, especially for long seeks.

Alas, I've never been able to find the paper again, nor can I remember it's title. Otherwise I'd point you towards it, and let you read it yourself.

AidanII
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