[maemo-users] 2Gb internal storage on N810

From: hendrik at topoi.pooq.com hendrik at topoi.pooq.com
Date: Sat Jun 27 17:41:29 EEST 2009
On Sat, Jun 27, 2009 at 12:40:32PM +0200, Nils Faerber wrote:
> And finally you should take the average number of write cycles until
> failure into account. All chips specify this and it means the average
> for per eraseblock. Numbers of 10.000 to 100.000 or even 1.000.000 are
> possible. Most filesystems used on NAND and also the controller chips in
> SDcards do wear levelling, which means they distribute the erase cyles
> over the chip / partition as much as possible. So with a 2GB SDcard and
> not too often writes the probability that the same eraseblock is erased
> again is pretty low and thus 100.000 cycles is a very long time -
> usually much much longer than the lifetime of the other parts of the device.

But when it does start to fail, it will probably have so many bad blocks 
that it fails completely.  THis kind of redundancy and error correction 
make a system resilient to damage, but also make it more brittle when 
it does start to crack.  Backups are always useful.
> Finally this may also be an interesting reading:
> 	http://en.wikipedia.org/wiki/Flash_memory
> > Is there any difference in speed if I get a microSD card and use it with
> > the miniSD adapter as opposed to getting a miniSD card? The reason for
> > getting microSD is that I can use it on more of my devices...
> This depends on the controller chip, chip type and chip organisation
> (interface width) used in the card. I do not think that there is a
> general rule that micro SD is faster or slower. It is interfacewise
> completely identical to a big SDcard and can run on the same clockrates etc.

What does matter is the so-called category of the SD card, which is a 
measure ot its speed.  The "category" is usually a number written inside 
a C on the card itself.  More is better.  I think the N800 can benefit 
from SD speed up to category 6 or 8 or so.  I don't know if the N810 is 
different.  I have category 6 8G cards in my N800.

Category 2 cards sold in drug stores (and even some mass-market 
consumer electronics dealers) seem to have similar prices to category 6 
cards at on-line computer-electronics dealers.  There's an enormous, and 
largely random, variation in prices even within one retail store.  It's 
worth shopping around.

-- hendrik
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