[tahoe-dev] [tahoe-lafs] #964: List sizes for storage using base-2 sizes, not base-10

tahoe-lafs trac at allmydata.org
Sun Feb 21 05:30:35 UTC 2010

#964: List sizes for storage using base-2 sizes, not base-10
 Reporter:  USSJoin       |           Owner:           
     Type:  defect        |          Status:  new      
 Priority:  minor         |       Milestone:  undecided
Component:  code-storage  |         Version:  1.6.0    
 Keywords:                |   Launchpad_bug:           

Comment(by zooko):

 We generally prefer base-10 arithmetic, because it is easier for users to
 use. For example, if you ask my mom how many 20-byte things she can store
 in a 2-terabyte bucket, she'll probably ask "What's a terabyte?", and if
 you tell her it is a trillion bytes, she'll say "Then I can store 100
 billion of them.". If instead you tell her that it is 2^40^ bytes, then
 she'll either have to get out a calculator or she'll just give up.
 In fact, I strongly suspect that a similar problem applies to computer
 hackers as well as to moms. Quick, how many 20-byte things can you store
 in a bucket of size 2^41^ bytes (two
 [http://en.wikipedia.org/wiki/Tebibyte TiB])? I think it will take you
 longer to answer that question that it would take my mom to answer the
 base-10 variant of the question.
 If you answered "about a hundred billion of them" then your answer was 10%
 Back when our buckets were on the order of thousands of elements in size,
 the approximation of 2^10^≅10^3^ was only 2.5% off. The approximation of
 2^20^≅10^6^ is 5% off, 2^30^≅10^9^ is 7.5% off, and 2^40^≅10^12^ is 10%
 By the way, Apple products now report file sizes and filesystem spaces in
 base-10: http://support.apple.com/kb/TS2419

Ticket URL: <http://allmydata.org/trac/tahoe/ticket/964#comment:4>
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