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Date: Tue, 18 Oct 2011 10:42:22 +0200
From: Ivan Djelic <ivan.djelic@parrot.com>
To: Ricard Wanderlof <ricard.wanderlof@axis.com>
Subject: Re: UBIFS recovery fails
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Cc: "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
	Artem Bityutskiy <dedekind1@gmail.com>
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On Tue, Oct 18, 2011 at 09:11:54AM +0100, Ricard Wanderlof wrote:
> 
> On Mon, 17 Oct 2011, Artem Bityutskiy wrote:
> 
> > [...] Unfortunately, no one really invested time into making UBIFS 
> > support MLC very well. It needs some more work. It also have some issues 
> > related to unstable bits in modern SLC.
> >
> > In short - if you want to use UBIFS on MLC - you should not have unclean
> > reboots. If you want to make UBIFS 100% uclean-reboot save on MLC - you
> > need to work on it some more.
> >
> > We (the original authors) developed and tested it on very robust SLC
> > NAND.
> 
> Do you have any specifics on what the issues are with MLC ?
 
Besides unstable bits, lower endurance, higher ecc requirements and NOP1, there
is a "page pairing" phenomenon which is not handled by UBI/UBIFS AFAIK.
When you cut power during a page write, you may lose data in another (paired)
previously programmed page.

BR,
--
Ivan