[linux-lvm] I'm confused

[William Blunn]

> I think hardisk manufacturers use base 10, rather than base 2,
> when they speak of "mega" and "giga", ie. mega = 1000K and not
> 1024K. That means that a 120G hardisk is only 114.4G.

No.

You are right in that "mega = 1000K", but from your figure of 114.4, you
still appear to have "K = 1024" and "G = 1024M", both of which are
wrong.

Hard disk manufacturers use SI defined multipliers, i.e. they use a
documented standard.

  K = 10^3
  M = 10^6
  G = 10^9

  120 GB = 120 000 000 000 B

Computer people have traditionally abused these symbols to mean
multipliers with similar values, but based on powers of two.

Symbols have been defined for these multipliers, but some people still
haven't caught up to them.

  Ki = 2^10 = 1024
  Mi = 2^20 = 1048576
  Gi = 2^30 = 1073741824

So

  120 GB ~= 111.8 GiB

Interestingly, LVM1's vgdisplay incorrectly uses "GB" in its output
where it should say "GiB".

Bill
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William H. Blunn - <bill+s.9sfuw6uo at tao-group.com> - Developer Support
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