Disk geometries

D Yuniskis · 2010-06-10T17:47:09+00:00

Hi,I'm wondering what factors drive disk geometries (and, thus,capacities). I.e., what makes certain sizes common andothers less common (e.g., you never? saw 7GB disks).Of course, the sizes of the magnetics determine the sizes of themagnetic domains that can be resolved, etc. But, I don't seeanything else in the design of a disk system that forcescapacities to the values that are commonplace.E.g., semiconductor memory has reasons for wanting to besized in powers of two -- there is no manufacturing advantageto making a 5KB device (e.g.). If a foundry can improve itsprocess, it can make a *smaller* 4KB device and (hopefully)improve market share, profit margin, etc. that way. Ultimately,make an 8KB device that's the size of the old 4KB device, etc.But, disk platters are fixed sizes (?). There are no economies (?)to be gained by shrinking platter sizes as your magnetics improve.There are no "standards" (e.g., like with removable media) thatforce the magnetic domains to be of a particular size.(you can pursue this reasoning to considerable depth)So, why don't we see disks with 7% more capacity as magneticsshrink by 7% (e.g.)? Or, is it just not economical to retoolfor anything less than a 2X capacity increase?--don

Jun 10, 2010 41 Replies

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Archimedes' Lever 16 years ago

Shame that you aren't standing in front of four of them, like another asshole just like you is today.

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krw 16 years ago

Ah, isn't little Dimmie cute. Now run along and play in the freeway.

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