Hi Jim,
Thanks for sending that out. After reading page 3 it looks like the card
maintains a pool of available addresses per zone and uses a new one for each
new write. When the available pool of 3 % per zone is used up the card will
fail. The wear leveling is not over the entire card as of October 2003 the
date of the document. If this is true for a current card the OS would have a
direct influence on life if it used the same zones for data writes. Most of
the current flash are the multiple bits per cell. This may have a much more
robust scheme. I have not been able to wear out any SD card yet, but all of
mine are made in the last 2 years. We should be able to make a simple wear out
tester to find out what the real limits are on specific cards. This testing
would be limited to cards of the same lot.
Bobby
----- Original Message -----
From: Jim Donelson
To: uClinux development list
Sent: Thursday, March 26, 2009 5:27 AM
Subject: Re: [uClinux-dev] SD card corruption upon reboot and de-power
:
Jim Donelson wrote:
-If we are talking about regular SD cards, there is no internal wear
leveling.
It is up to the driver to do that.
I was wrong about that, there is internal wear leveling.
Read this:
http://www.sandisk.com/assets/file/oem/whitepapersandbrochures/rs-mmc/wpaperwearlevelv1.0.pdf
I also reviewed the interface spec, and there is not documented way to reset
it.
There seems to be much hand waving here too about how it actually does this,
and what would happen if you remove power while these operations are in
progress.
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