Using standardized SI prefixes

Scott James Remnant scott at ubuntu.com
Wed Jun 13 13:29:39 UTC 2007


On Wed, 2007-06-13 at 12:51 +0200, Christof Kr├╝ger wrote:

> On Tue, 2007-06-12 at 15:52 +0100, Ian Jackson wrote:
> > shirish writes ("Using standardized SI prefixes"):
> > >       Please look at http://en.wikipedia.org/wiki/Binary_prefix .
> > 
> > Urgh, these things are ugly and an abomination.  We should avoid them.
>  
> I'd really like to hear some real arguments against SI prefixes, besides
> being ugly or funny to pronounce or just because "it has always been
> like that". Advantages of using SI prefixes has been mentioned in this
> thread. Please tell me the disadvantages so there can actually be a
> constructive discussion.
> 
User Confusion.

Most users do not know what a "tebibyte" is, and they do not care.  They
know that "a terabyte" is "about a million million bytes", and that is
sufficient.

Since you're rounding anyway, the loss of accuracy between "about a
million million bytes" and "just over a million million bytes" is not
significant.  Certainly not at the expense at having to teach users
another new unit.

Hard drives are bought in gigabytes, memory is bought in gigabytes, etc.
Quoting the same figures with a different unit in the operating system
is pedantry for its own sake.

Users have already learnt that the term "gigabyte" is approximate.

Introducing new units has only added confusion, rather than removed it.

Before the new units, we all knew that 1GB was an approximate figure and
likely to be (for bytes) based on a power of 2.  Now we have figures
quoted in GB and GiB, some of which are power of 10, some of which are
power of 2.  Some figures quoted in GiB are wrong, and should be in GB;
likewise some in GB should be GiB.  And we still have many figures in
both GB and GiB which are neither of the two!

Renaming the 1.44MB floppy helps in neither case; it is neither 1.44MB
or 1.44MiB.  One could name it the 1.4MB or 1.47MiB floppy and confuse
everyone into thinking it's a different thing, of course.  Or maybe it
should be the 1,440KB floppy, or the 1,475KiB floppy?  Neither of these
help the situation.

Without the binary unit to consider, when we quote a drive as 1TB, we
know that it has *at least* 1,000,000,000,000 bytes available.
Depending on the drive, it may have anywhere between this and
1,099,511,627,776 bytes available.  It's actually more likely to have
something strange like 1,024,000,000,000 available.

(And none of this takes into account partitioning and filesystem
overhead!)

I see no problem with this "1TB" quote being approximate.  It's rounded
anyway.  If you really want to know how many bytes are available, you
can use this great unit called the "byte" which is accurate and not
subject to change[0].

Scott

[0] Unless you're older than 25.
-- 
Scott James Remnant
Ubuntu Development Manager
scott at ubuntu.com
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