To: linux-kernel@vger.kernel.org
From: Lutz Vieweg <lvml@5t9.de>
Subject: Improving SD/SDHC/SDXC write performance by using a discard/TRIM
 like operation
Date: Mon, 04 Jun 2012 20:27:01 +0200
Message-ID: <jqiull$fvb$1@dough.gmane.org>
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When I read reports from (non-expert) users who claimed that they were able
to restore the initial write performance of their SDXC cards by using a "special
formatter tool" (while normal "formatting" did not improve performance),
I was very sceptical, as I also had read that there is no way to discard/TRIM
blocks on SD/SDHC/SDXC cards.

But then I noticed that this "special formatter" tool was actually offered (for free)
by the SD Association:
  https://www.sdcard.org/downloads/formatter_3/
... and its documentation clearly states that this tool is capable of using
"flash erase" operations on SD cards, which are said to be different from
ordinary "overwrites", see
  https://www.sdcard.org/downloads/formatter_3/SDFormatter_3.1e.pdf
pages 7 ("Format type Erase" vs. "Format type Overwrite") and the screen shot on page 9.

Now I wonder: Is there really such a thing as a command to erase NAND flashes
in SD cards like there is for SSDs? If so, it would certainly be a good thing
to support it with Linux block discard...

Regards,

Lutz Vieweg

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