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Bigger hard drives

WildW

WildW

Senior member
Okay, time for a stupid question. Why don't they make bigger hard drives? Specifically, why the 3.5 inch size - most computers have spare 5.25 inch bays after all.Think of the advantages. . .

Capacity: you could have about 1.5 times the disc radius. Surface area increases with the square of radius, so over twice the capacity per platter of a 3.5 inch drive.

Speed: For a given rotational speed the average linear speed at the heads will be greater.

Cooling: 5.25 inch bays are on the front of the PC - you could possibly integrate some cooling with air from outside the PC case.


Is there some obvious reason why not - like maybe "90% of drives end up in datacentres in 1U servers where a bigger drive wouldn't fit, so the cost would be prohibitive."
 
Is there some obvious reason why not - like maybe "90% of drives end up in datacentres in 1U servers where a bigger drive wouldn't fit, so the cost would be prohibitive."
Click to expand...
Yep... actually they re mostly 2.5 inch... which is already trickling down... the velociraptor for example is the right size, except thickness...

Larger drives mean much longer seek rates as the heads have to move further... degrading performance. People want their drives to be fast.
There is also the issue of justifying the price.
And the fact that the controller is not all that expensive. So mainly you are paying for platters. And it makes more sense to just use two drives in raid than it does to make a physically larger drive with more / larger platters.

Rotational speed is also really not that big of a deal anymore compared to other factors... the major limitation for speed is not the speed of rotation.
 
Yes, seek times would be a pain I suppose, that's what I'd missed.

I figured it'd be a cheap way to get bigger continuous storage sizes, particularly for archival of seldom used data, especially large files e.g. video, where seek wouldn't be an issue.

I suppose enterprise doesn't mind paying out for "proper" storage solutions so it's a non-issue for them.


Not sure if the plywood comment was meant to be sarchasm or not. I'm just going to assume that you already have some free slots in your application for 8x10 plywood. I never use more than one of my external drive bays, such a waste 🙂
 
Originally posted by: WildW
Okay, time for a stupid question. Why don't they make bigger hard drives? Specifically, why the 3.5 inch size - most computers have spare 5.25 inch bays after all.Think of the advantages. . .

Capacity: you could have about 1.5 times the disc radius. Surface area increases with the square of radius, so over twice the capacity per platter of a 3.5 inch drive.

Speed: For a given rotational speed the average linear speed at the heads will be greater.

Cooling: 5.25 inch bays are on the front of the PC - you could possibly integrate some cooling with air from outside the PC case.


Is there some obvious reason why not - like maybe "90% of drives end up in datacentres in 1U servers where a bigger drive wouldn't fit, so the cost would be prohibitive."
Click to expand...

Two big reasons:

1. Bigger discs = longer distance for read/write heads to travel = slower access times

2. Bigger discs = more mass =more inertia = more power to spin up = bigger actuator arms = more heat = more power

So smaller HD's means smaller arms that travel less and require less power, and produce less heat.
 
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