New SI prefixes clear the way for quettabytes of storage

The range of prefixes used within the International System of Units (SI) has been expanded with new names covering very large and very small numbers, driven in part by the ballooning requirements of data storage in some sectors such as data science.

According to the UK’s National Physical Laboratory (NPL), these changes were approved at a recent meeting of measurement scientists and government representatives from around the world at the 27th meeting of the General Conference on Weights and Measures (CGPM).

The move introduces two new prefixes at the top end of the SI range and two at the bottom end that can now be used to express measurements worldwide, and is understood to the first expansion to the SI prefix range since 1991. The proposal was led by Dr Richard Brown, Head of Metrology at NPL.

Those new names are ronna (symbol R) for 1027 and quetta (symbol Q) for 1030, while their counterparts at the opposite end of the scale are ronto (symbol r) for 10−27 and quecto (symbol q) for 10−30.

In the rather convoluted language of the resolutions issued by the CGPM, it noted that “decisions were made at previous meetings when it was considered timely to extend the range of SI prefixes,” and listed times when this had happened before in 1960, 1964, 1975 and 1991.

It went to say that the decision had been made in consideration of “the needs of data science in the near future to express quantities of digital information using orders of magnitude in excess of 1024” (which would be a yottabyte).

Also, the resolution noted the need for “the importance of timely action to prevent unofficial prefix names being de facto adopted.” Or in other words, the CGPM is getting in early before anybody else decided to coin names for what would come after a yottabyte of storage.

According to the NPL, the change was largely driven by storage applications already starting to use prefixes at the top of the existing range (yottabytes and zettabytes) for expressing huge quantities of digital information.

We look forward to hearing from storage vendors who can promise us a quettabyte of capacity, although this may take a while, since cloud storage provider BackBlaze detailed earlier this year that its platform currently has just over two exabytes of total data storage under its management, which is about two trillionths of a quettabyte. ®

SourceThe Register

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