On Wed, Feb 18, 2015 at 10:44:58AM +1300, IVP wrote:
> > let the controller refresh the charge
>=20
> Thanks, I didn't know that
>=20
> When you say "refresh the charge" do you mean just power it
> up or actually re-write all the data ?

The flash cells store a charge.

Powering the device won't necessarily refresh the charge, it depends
on the firmware.  Without seeing the firmware, you can't be sure,
unless you probe the interface between the controller and the flash
chip.

However, reading the data must refresh the charge, because reading
without refreshing is destructive to the charge.

Writing will erase cells and set the charge anew.  The controller will
not necessarily use the same cells that held the same disk blocks;
there's a performance advantage in using a queue of pre-erased flash
blocks.

(My comments above are mainly for high density flash, in the several
gigabit range.  Very low density, as used in SPI flash chips attached
to microcontrollers or microprocessors for firmware or configuration
state, have somewhat different problems.  ;-)  With much clearer
datasheets.)

> That would be a pain and more hassle than copying a DVD every few
> years

You get other problems with DVDs.

My first worry is whether the drives will continue to work, and if
they'll continue to be available for purchase.  I'm already unable to
use particularly old CD-R media, against new drives, as the standards
and capabilities have changed.

For the moment, I use hard drives, and replace them every year or two.

I don't expect them to last, either.

The other trick is to divide things between archive and ephemeral, and
don't let the archive data set grow too much.

The next Carrington Event will be interesting.

--=20
James Cameron
http://quozl.linux.org.au/
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