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Kryder's law
In computing, Kryder's law states that hard drives are benefiting from an exponential increase in the density (bits per unit area) of information they are able to store. Kryder's Law is essentially Moore's Law for storage. This is true, although the numbers associated with Kryder's Law resulted from a misreading of a SciAm article and some bad math and, as such, vastly misrepresent the true rate of growth. Kryder's Law states, incorrectly, that the density of information on hard drives has been growing at an even faster rate than Moore's Law would predict, increasing by a factor of 1000 in 10.5 years, which corresponds to a doubling roughly every 13 months.
Kryder's law arose from a misreading of a Scientific American article which purportedly said hd capacity had increased 1000 fold every 10.5 years. These numbers were duly crunched and it was discovered that, according to the [incorrect] numbers, hd capacity was actually doubling every 13 months, significantly faster than Moore's Law would predict. This error was pointed out on http://www.mattscomputertrends.com/Kryder's.html, and on April 9th posted to slashdot. It has, actually, not corresponded at all to either this law or Moore's Law, but rather appears to be much slower. The article actually states that in 1956 we had 2000 bits/sq. inch and in 2005 we had 100 billion bits/sq. inch. Beginning from the 2000 bits/sq. inch in 1956 and progressing to the 100 billion bits/sq. inch found at the time of the article's publication (2005) is a 50 million fold increase. Moore's law would suggest that, after thirty two 18 month periods between 1956 and 2005, we would have had a 10^32 fold increase, or 8.5 trillion bits/sq. inch.
It has been suggested that Kryder's Law originated from the publication of this Wikipedia page, and this page remains in the hope that it will help to correct the incorrect information. The remainder of the page remains intact from before this error was realized.
The ongoing increase in information density has resulted in an exponential decrease in the cost of computer disk drives. This has enabled the commercial viability of consumer products that require large storage capacities, such as the Apple iPod digital music player, the TiVo personal video recorder, and Google's Gmail web-based email program.
This is also gradually but significantly altering how programmers think: in many programming tasks there is a time-space tradeoff, so as space becomes cheaper and cheaper relative to CPU cycles the appropriate choice about time versus space changes. For instance in database work it is now common practice to store precomputed views, transitive closures, and the like on disk in order to speed up queries; 20 years ago such profligate use of disk space would have been impractical.
The law is named after Mark Kryder, a Seagate Technology engineer who has been on the cutting edge of storage research.
Future of Kryder's law[edit]
If current rates of growth are maintained then within two decades, a consumer will be able to store all of the creative works produced by every member of the human species in a $100 storage device, including realtime video capture of ones entire lifetime. The only current applications that may outstrip these storage requirements are physics systems such as weather simulations and high energy particle accelerators -- and perhaps some very large video image databases.
Possible developments that may sustain Kryder's law include faster access times, increased throughput and smaller form factors.
Access times haven't kept up with throughput increases which themselves haven't kept up with growth in storage capacity. The main way to increase either is to increase the number of read-write heads in a hard drive. Since flying heads are the most expensive component of hard drives, increasing their number per hard drive wouldn't help Kryder's law. Currently, the most promising way to increase access times and throughput are with some form of nonvolatile RAM or holographic technology.
Form factors are a different matter. Ever smaller hard drives, preferably consuming smaller amounts of power, are an important technology for mobile computing. So it is likely that these applications will sustain Kryder's law in the near term.
See also[edit]
External links[edit]
- Scientific American article on Kryder's Law
- Behold the God Box - Less's Law and future implications of massive cheap hard disk storage
- Table of hard disk capacity over the past 25 years
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