[sf-lug] drive sizes/capacities: Re: Want a large Flash Drive or a good sized SSD?

[Michael Paoli]

Blame it (mostly) on marketing - and consumers not demanding better.

I think you've got that also about bass ackwards.

128 GiB !~= 117 GB
It's more like the other way around:
128,000,000,000 bytes =~ 119.209289550781 GiB

https://en.wikipedia.org/wiki/Binary_prefix
https://en.wikipedia.org/wiki/Metric_prefix

And, why would marketing/sales do that?  Because it "sounds"
bigger (but isn't) and cost them less to make (less bytes).

Let's look at the #s, and % comparing decimal to binary:
$ perl -e 'for(1..5){my $i=(10**3)**$_;my $b=(2**10)**$_;print(join(q(  
),$i,$b,$i*100/$b.q(%),),"\n",);};'
1000 1024 97.65625%
1000000 1048576 95.367431640625%
1000000000 1073741824 93.1322574615479%
1000000000000 1099511627776 90.9494701772928%
1000000000000000 1125899906842624 88.8178419700125%
$

You can also look at the exact size of the device using the
/sys filesystem ... though it will give you size in 512 byte
blocks:
$ (cd /sys/block && grep . /sys/block/sd[a-z]/size)
/sys/block/sda/size:4004704368
/sys/block/sdb/size:312581808
$

E.g., have a look at the drives on:
https://www.wiki.balug.org/wiki/doku.php?id=balug:offered_wanted_hardware_etc
And notice a particular pattern ...
what's marketed as 80GB is at or just a bit larger than
80*10^9 bytes, well short of 80*2^30 bytes.
Likewise for 1TB:
at or very slightly over 10^12 bytes, well short of 2^40 bytes,
etc.

That's also why the marketing materials tend to have their little
CYA *, e.g. stuff like:
1TB*
*TB=1,000,000,000,000 bytes

> From: "Bobbie Sellers" <bliss-sf4ever at dslextreme.com>
> Subject: [sf-lug] Want a large Flash Drive or a good sized SSD?
> Date: Mon, 14 Jan 2019 10:45:22 -0800

>     Well the drives of course are not quite as large as labeled
> the 128 GiB USB Flash Drive comes in at 117.x Gigabytes but the
> price is right.
>     I bet the 128 and 240 GiB drives come in below the
> labeled size but the prices are good.