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Hard Drive Speed - You need to put your $0.02 cents in on this one

B

BCinSC

Platinum Member
Theoretically, the outer tracks of a drive should be faster because while the spindle rotates at 5400, 7200, 10K, or even 15K RPM, the outer edge is going under the heads faster (someone provide the calculation - I'm too brain fried at the moment). Now all the various benchmark tests show drive slowly drop off as the heads move further out and most defrag programs that move files, put the most frequently used at the inner tracks. So why are the drives makers wedded to the 3.5in format? And why are 2.5in drives not produced at higher RPM?

I'll add more thoughts after some replys
 
I believe on a hard drive, the data is recorded on the outer most tracts first, opposite to a CD. Also, if the drive was 5.25", the seek times would increase since the head now has to, on average, travel a longer distance to access files.
 
Shmorq is correct about where the data is put and why. On a hd, the outer edge is moving faster than the inner, all the newer defrag programs will setup the data that you use most to the outer edge so that it is accessed faster.
 
The linear velocity of the outside tracks on a hard drive are quite a bit faster than the inside. Obviously the outside doesn't rotate any faster, that would be an interesting feat. Windows and every OS as far as I know writes from the outside of the disk to the inside. CD's write from the inside out, while DVD's can write either from the inside or the outside. When you see a defragger screen, the picture is reversed, the top of the window is the end of the drive going to the bottom of the window which is the inside of the drive. IDE only come in a 3.5" form factor however SCSI 10k drives are 3" and the Cheetah X15 is 2.6". The smaller diameter increases seek time which is more important than STR is most cases. The 2.5" platters are basically limited to laptops where power and heat plays a very large role, which currently limits them to 5400rpm.
 
Actually Pariah, this I know for sure, owning numerous SCSI 10K drives and the Seagate X15, they are usually 3.5" and the X15 is 3", per Seagate's own doc. As for outide and inside tracks, the consensus appears to correct my theory that it wrote from the inside-out. Thank you.
 
All 10k and 15k SCSI drives are 3.5" form factor, which does not mean 3.5" platter.

I pulled this off the SR X15 review:

"The manufacturer has thus reduced the platter size of the Cheetah X15 to about 2.6 inches, down from the 10k rpm standard of 3.0 inches"

I'm not sure which Seagate doc you were looking at, because I couldn't find any reference to platter diameter on Seagate's site. I own an X15 and Atlas 10KII and didn't get any useful documentation with them. I have no intention of taking them apart to see what size the platters are either.
 
On a semi related note, why do they not make 10 or 15k rpm IDE hard drives. Is it ATA interface unable to handle it? It seems that ATA 100 could handle 10 or 15k rpm without many bottlenecks, especially on random reads. Are IDE controllers not fast enough to keep up with a 10k or 15k drive or what? 7200 rpm's are so 90's.
 
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