<a href="http:&#x2F;&#x2F;www.tarsnap.com&#x2F;picoUSD-why.html" rel="nofollow">http:&#x2F;&#x2F;www.tarsnap.com&#x2F;picoUSD-why.html</a><p><pre><code>  There are three major reasons why Tarsnap pricing is defined in terms of picodollars per byte rather than dollars per gigabyte:

    Tarsnap&#x27;s author is a geek. Applying SI prefixes to non-SI units is a geeky thing to do.
    If prices were listed in dollars per GB instead of picodollars per byte, it would be harder to avoid the what-is-a-GB confusion (a GB is 10^9 bytes, but some people don&#x27;t understand SI prefixes). Picodollars are perfectly clear — nobody is going to think that a picodollar is 2^(-40) dollars.
    Specifying prices in picodollars reinforces the point that if you have very small backups, you can pay very small amounts. Unlike some people, I don&#x27;t believe in rounding up to $0.01 — the Tarsnap accounting code keeps track of everything in attodollars and when it internally converts storage prices from picodollars per month to attodollars per day it rounds the prices down.</code></pre>