Re: RAID Sizes (was Re: Why do people in the UK put a u in the word color?)

[Andrei Popescu <andreimpopescu@gmail.com>]

On Fri, 14 Apr 2006 08:06:53 -0700
Paul Johnson <baloo@ursine.ca> wrote:

> On Friday 14 April 2006 03:02, CaT wrote:
> > On Thu, Apr 13, 2006 at 09:18:17AM -0400, Matthias Julius wrote:
> > > > On Wed, 2006-04-12 at 12:32 -0400, Matthias Julius wrote:
> > > >> Yes, there is.  As example here is part of the output of mdadm:
> > > >>
> > > >>   Array Size : 468872448 (447.15 GiB 480.13 GB)
> > > >>   Device Size : 156290816 (149.05 GiB 160.04 GB)
> > > >>                                   ^^^        ^^
> > > >>
> > > >> Note there is GiB (gibibyte) which is 1024 MiB (mebibyte) and there is
> > > >> GB (gigabyte) which is 1000 MB (megabyte).
> > > >
> > > > If GB is decimal, then why aren't the sizes
> > > >     468.87 GB
> > > >     156.29 GB
> > >
> > > Why should they be?
> >
> > Because dividing by a multpile of 10 essentially simply moves the
> > decimal point to the left. The thing that's not bleedingly obvious
> > there though is that 156290816 is in kibibytes. :) So:
> >
> > 156290816 * 1024 / 1000 / 1000 / 1000 ~= 160.04 GB :)
> 
> You're getting your sizes confused, you either use base 2 or base 10, not 
> both.  1024/1024/1024/1024 is the right equation.

It was just right. This is more in detail:

	156290816(kiB) * 1024 = 160041795584 bytes

160041795584/1000/1000/1000 ~= 160.04 GB

or

160041795584/1024/1024/1024 ~= 149.05 GiB

Andrei
-- 
If you can't explain it simply, you don't understand it well enough.
(Albert Einstein)