Supersonic Disk Drive Is A Myth

The idea that disk drives haven't gotten faster than 15K RPM because it would mean disks would have to become supersonic isn't true. What's the real reason?

Howard Marks

January 27, 2014

1 Min Read
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Over the past few weeks, I've heard folks promoting solid-state storage solutions and repeating the myth that spinning disks haven't gotten faster than 15K RPM because it would mean that the airflow over the heads would become supersonic. While it's a good story, and the thought of little tiny sonic booms inside a disk drive is amusing, there's very little truth behind it.

For anyone who remembers his or her high school math, it's pretty simple to calculate the linear velocity of the outer edge of a spinning disk. Here's the formula, where LV is the linear velocity and RV is the disk's rotational velocity:


LV=D*π*RV

Of course, since nominal disk diameters are normally given in inches and rotational velocities in RPM, the formula above will give its results in inches per minute. To convert to miles per hour, divide by 63360 (the number of inches in a mile) and multiply by 60, which I assume you remember is the number of minutes in an hour.

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About the Author(s)

Howard Marks

Network Computing Blogger

Howard Marks</strong>&nbsp;is founder and chief scientist at Deepstorage LLC, a storage consultancy and independent test lab based in Santa Fe, N.M. and concentrating on storage and data center networking. In more than 25 years of consulting, Marks has designed and implemented storage systems, networks, management systems and Internet strategies at organizations including American Express, J.P. Morgan, Borden Foods, U.S. Tobacco, BBDO Worldwide, Foxwoods Resort Casino and the State University of New York at Purchase. The testing at DeepStorage Labs is informed by that real world experience.</p><p>He has been a frequent contributor to <em>Network Computing</em>&nbsp;and&nbsp;<em>InformationWeek</em>&nbsp;since 1999 and a speaker at industry conferences including Comnet, PC Expo, Interop and Microsoft's TechEd since 1990. He is the author of&nbsp;<em>Networking Windows</em>&nbsp;and co-author of&nbsp;<em>Windows NT Unleashed</em>&nbsp;(Sams).</p><p>He is co-host, with Ray Lucchesi of the monthly Greybeards on Storage podcast where the voices of experience discuss the latest issues in the storage world with industry leaders.&nbsp; You can find the podcast at: http://www.deepstorage.net/NEW/GBoS

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