Sign in with
Sign up | Sign in
Your question

Why not 5.25"?

Last response: in Storage
Share
December 17, 2006 2:39:07 PM

We keep on hitting storage barriers with 3.5" hard drives. Now, we have to go the next step with perpedicular recording, which keeps storage densities rising, but eventually yes we will hit the barrier we were expecting to hit.

So why doesn't anyone make 5.25" hard drives?

The PC infrastructure is already in place, many computers nowadays come with empty 5.25" bays that aren't used. The 5.25" hard drive could keep with the SATA standard, but obviously having 5.25" of horizontal space makes for larger platters and solving storage issues quite easily.

So why not?

More about : question

December 17, 2006 3:26:17 PM

Quantum already tried this with their "bigfoot" drives. Good solid drives, but they lacked in performance. Eventually they just faded away. I dont think anyone will try it again, the performance hit is to much and sales wont go anywhere without good performance. Especially considering how easy it is to set up a raid to match capacity and keep most of the performance.
December 17, 2006 3:32:25 PM

IT maybe useful for very large storage, but not speed, considering the physics involved
Related resources
December 17, 2006 4:20:17 PM

so if smaller sizes mean better performance, why doesn't someone make a 2.5" drive for desktops with like 25000 RPM for enthusiasts with only like 30 GB but it serves as a boot drive, kinda like the original raptor but faster in a 2.5" or similar for desktops? Sure there are SCSI add-in cards but I have few enough expansion slots, PCI or PCI-E, to add another card.....
December 17, 2006 4:36:55 PM

Quote:
so if smaller sizes mean better performance, why doesn't someone make a 2.5" drive for desktops with like 25000 RPM for enthusiasts with only like 30 GB but it serves as a boot drive, kinda like the original raptor but faster in a 2.5" or similar for desktops? Sure there are SCSI add-in cards but I have few enough expansion slots, PCI or PCI-E, to add another card.....


It's not that simple. There are many factors that go into hard drive performance, and many constraints that limit that performance.

One of the reason the 5.25" hard drive doesn't perform so well is the long seeks. The head moves much further on a 5.25" platter than on a 3.5" platter, slowing the seek times. Another reason is that with the large 5.25" platters, you can't spin them as fast and maintain proper balance. 5400 RPM is near the limit -- this slows the rotational latency times.

On 2.5" drives, you have some limitations in speed because of heat constraints. Laptops run their components near the thermal limits in order to prevent using unecessary power on cooling fans. In this condition, you can't use a hard drive that will produce a lot of heat. This means slowing down the access speed of the head in software, and reducing rotation speed to 7200 RPM or less. These things limit performance. Also, moving the head faster and/or spinning the drive faster uses more power, which is at a premium in a laptop.

3.5" drives are the sweet spot. In a well-ventilated desktop, there aren't these constraints on power or heat. Further, the form factor of the 3.5" drives allows multiple platters, which increase capacity. And 3.5" drives can be made to spin at (currently) up to 15K RPM.

The next generation of drives meant to be just the boot drive, with outstanding speed, low power & heat characteristics, but not a lot of capacity will be flash-based devices.
December 17, 2006 4:40:12 PM

Quote:
why doesn't someone make a 2.5" drive for desktops with like 25000 RPM for enthusiasts with only like 30 GB but it serves as a boot drive,


Maybe because at those speeds, the outer rim would be going well over supersonic speeds, if my calcualtions are correct. I doubt any company would like the liablity problems that might be caused if such a drive fragmented at such high speed.
December 17, 2006 8:32:31 PM

I said "like" for a reason... lol.

Thanks for the explanations everyone! :) 
December 17, 2006 9:12:00 PM

soon enough flash memory of some kind will replace hard drives.. then size wont matter at all
December 17, 2006 9:35:11 PM

I oftened wondered why some manufacturer didn't create a disk drive with two actuator arm assemblies, one on each side of the platter stack. That way you could access data at two points simultaneously. Add in a larger cache, say a nice fat 128MB flash chip, and you'd get great performance. You could even add in some logic like native command queueing so that the two assemblies accessed the data efficiently.

Well there might be some problems with timing, but that's what the cache is for. Other problem would be power consumption and of course more points of failure.
December 17, 2006 9:54:31 PM

Maybe someday 2.5" harddrives will make it to the desktop.


http://www.dailytech.com/article.aspx?newsid=5098


"Seagate is quick to point out that its Savvio drives differ greatly from other 2.5-inch notebook drives. The Savvio line was designed from the ground up as an enterprise class drive, sharing more in common with the Cheetah than the Momentus."
December 17, 2006 10:43:06 PM

I think if a company was to design a 2.5 HDD for a desktop, power and heat would not be as problematic as in a laptop. But in turn, acoustics could pose an obstacle as well.

I agree that 3.5” in the sweet spot, especially from an economical stand point, as Dirian pointed out.
December 17, 2006 10:52:27 PM

A few things have to be improved for that day to come.

Right now Solid State Disks are behind HDD in storage capacity and burst rates (although their seek times are significantly better), not to mention their pricing is way higher.

For everything else SSD’s win.
!