[LMB] AKICOTL: Technical question OT:

[James]

On Jan 23, 2008 5:14 AM, Ed Burkhead <edburkhead at insightbb.com> wrote:
> I normally don't like taking things back to the store, but if the 8GB flash
> drive won't hold the 7.9GB files you bought it for, perhaps . . .

Actually two things.

1) Storage companies use the SI meanings of words, while OSes
generally report the incorrect meaning. So you could be copying 7.9GiB
of data to a 8GB disk. That won't work. (Most OSes report the base-2
version. Linux has however adopted the proper meaning for most of its
utilities and reporting.)

2) 8GB flash means it has 8GB chip in there. However, because this
flash can go bad, or be bad from the factory, 2% is reserved for bad
blocks and spares for blocks that go bad. This means you lose 160GB
off the top. Then you have to add in the overhead for the flash
translation layer and wear levelling systems so you don't wear out
your flash chip prematurely, which generally can consume another 1-2%
of space. Add again another percent or two lost for the formatting,
and a good chunk of it's lost. (So even though memory is charged with
the base-2 amount, often using the SI value works when you count in
all the overhead).

Also, if it's a flash card like SD or Memory Stick, another few % is
used to hold the security area.

If you need to carry > 4GB files around, there's nothing to do but use
a good filesystem like NTFS. Generally you can yank it out since
Windows disables write caching to USB disks so it shouldn't matter,
other than the filesystem being marked as "dirty" because NTFS never
had a chance to properly unmount.

Or you can always use something like WinRAR and break the files into
2GB pieces, but that can be pain.

Generally though, I use the "Safely Remove Hardware" method since it's
universal across all operating systems, and generally the safest.

James