[Info-vax] disk sizes

[Phillip Helbig---undress to reply]

In article <ijr7p5$unj$1 at Iltempo.Update.UU.SE>, Johnny Billquist
<bqt at softjar.se> writes: 

> On 2011-02-20 14:57, Phillip Helbig---undress to reply wrote:
> > Standard hard-disk sizes are 1.07 GB, 2.1, 4.3 (or sometimes the more
> > precise 4.29---one rarely sees the more precise 2.15).  8.6 (8.59) is
> > also relatively common.  This is clear, since 1024^3=1073741824 and then
> > one has 2, 4 or 8 times this.  So far, so good.  After that, sizes tend
> > to be 9.1, 18 (18.2---though 17 (roughly twice 8.6) also exists), 36
> > (36.4), 73 (72.8) and 146.  These are also powers of two times the new
> > basic size, but where does the 9.1 basic size come from?
> 
> Are you aware that disk manufacturers tend to give disk sizes in powers 
> of 10, not power of 2, as this makes the disks look a bit larger?

Right, that is why 1-Gigibyte is marketed as 1.07 Gigabyte etc; see 
above.  My question is why the jump from 8.6 to 9.1?

> Besides, the disk geometry and sizes almost never means you end up with 
> something even divisble by any "sensible" numbers, what are you trying 
> to figure out here?

I just want to understand it.  :-|