Re: bug#17505: dd statistics output

[Linda Walsh]

Henrik Juul Pedersen wrote:
> Christian Groessler writes:
> > 268435456 bytes (256 MB) copied, ...
>
> This would be a clear violation of the SI standard, which says on its
> prefixes:
----
I've given this some though and now feel that the SI system is inappropriate
for computer base-2 units (bytes, (2^3 bits), and sectors (2^9 bits)).  It
has never been considered appropriate or intelligent to mix your bases,
but that is exactly what using base10 w/base-2 units is doing.

The SI  system was developed for physical units -- grams, meters, liters,
etc.

If they want to talk a physical quantity, bits would be appropriate.  But
as soon as they use "Byte", they are stepping into *base 2*.  Mixing
base-10 prefixes with a power-of-2 quantity would be bad form in any
scientific paper.  the SI committee telling the computer industry how they
should use 'KB', or MB.. is a bit like them telling the US what prefixes it
should use in front of inches, feet, yards...etc.  Does
putting kilo in front of 'yards', make it an SI unit?  how about
measuring liquids in milliquarts?  or weight in kilopounds.

I think anyone thinking about those examples would say it is insane to mix
power-of-10 prefixes with non-si units -- when was the last time you heard
population expressed in kilopeople or megapeople.

Either never or rarely,  because those are not physical units -- the
area of authority for the SI standard.

Bytes are not physical units, nor are 'sectors'. -- they are logical
amounts based a conceptual grouping of bits.  By using 'Byte' or 'Sector',
one is already using "base-2".  Switching to base-10 for larger prefixes
would be considered bad form in any other area -- yet that is what
the SI folks would foist upon the computer industry.


One *cannot* express disk space, accurately, with base 10 units.  Doing so
is inherently wrong -- and was intended to mislead from the very
beginning.  No disk manufacturer puts out disks where the number of bytes
on the disk is a power of 10.  disk space HAS to be a power of 2 on binary
computers.

Memory doesn't come in multiples of "10" bits or bytes.  It comes in
multiples of 2.  Using binary prefixes with binary units is consistent,
but buying into the propaganda that base10 units should be used with
binary units is just dumb.

> "These SI prefixes refer strictly to powers of 10. They should not be used
> to indicate powers of 2 (for example, one kilobit represents 1000 bits and
> not 1024 bits). The IEC has adopted prefixes for binary powers in the
> international standard IEC 60027-2: 2005, third edition, Letter symbols to
> be used in electrical technology – Part 2: Telecommunications and
> electronics. The names and symbols for the prefixes corresponding to 210,
> 220, 230, 240, 250, and 260 are, respectively: kibi, Ki; mebi, Mi; gibi,
> Gi; tebi, Ti; pebi, Pi; and exbi, Ei. Thus, for example, one kibibyte would
> be written: 1 KiB = 210 B = 1024 B, where B denotes a byte. Although these
> prefixes are not part of the SI, they should be used in the field of
> information technology to avoid the incorrect usage of the SI prefixes."
> [1, page 121]
----
   I disagree.  They have no jurisdiction.  They are a foreign entity 
trying
to force confusing units on the computer industry. 

   If they want to use SI prefixes on the singular unit "bit", I'm fine 
with that.
But mixing it with a base-2 unit is confusing, makes calculations 
confusing, and
results in imprecision in specifying binary quantities.