[Novalug] best hard disk setup for home file server?
pereira at speakeasy.net
Fri Oct 16 08:54:08 EDT 2009
>> Is there any advantage to 2.5" drives over 3.5" drives besides size?
> Same reason you don't want to buy a Harley. OK, so Harleys are Chick
> Magnets, and that reason alone might override the technical reasons.
> Bigger = more wasted motion. There is a limit on how fast you can spin
> big massive long stroke pistons as well as big massive disk platters.
> At some point, the outer cylinders reach the speed of light, relativity
> takes over, and you will have died of old age before your data arrives.
> Of course the data will also be compressed, but the drive will also
> start emitting gamma rays from the spindle, a violation of FCC rules.
> But seriously, the movable arm will have to be more massive and move
> farther. Basically, size, mass and motion are Bad, and Small is Good.
Actually, the speed at the outer edge of the disk, the rim speed,
is limited by the strength and density of the disk material, not by
the size of the disk. The same speed at the outer edge implies that
a smaller disk can spin faster than a larger disk, so that your data reach
the read head faster. A smaller disk has less material, so that it's
easier to spin up and the motor can be smaller. Both make the disk
The 3.5" disks have about twice the area of the 2.5" ones. As the read
heads get smaller and the bit density increases, a disk manufacturer
can choose between making the disk smaller and cheaper, and maybe more
reliable because of less wear and tear on the various parts, or more
capacity. You may need more disk space, but I'd rather go for lower
cost and more reliability.
I wonder what a real disk designer thinks. But, small is good, except
when it comes to salaries.
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