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Date: Fri, 19 May 2006 10:35:10 -0700
From: "marty fouts" <mf.danger@gmail.com>
To: "Jim Thompson" <jim@netgate.com>
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Cc: gnn@freebsd.org, freebsd-small@freebsd.org
Subject: Re: Flash File Systems or Translation Layers?
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On 5/18/06, Jim Thompson <jim@netgate.com> wrote:

> Your >=3D 64MB requirement also tends to 'signal' why you prefer NAND
> flash, as its much less
> expensive than NOR flash in similar densities.  Still, this "64MB"
> requirement makes for an expensive board.

TS7250, quantity 1, with 128mb NAND is < $200 US.  That's hardly
expensive. It's one of the cheapest ARM based development board that
I'm aware of.

> > Agreed.  But I think that NAND and NOR are enough different that they
> > need to be supported differently.
>
> Perhaps, thought I will allow that JFFS2 can deal with both, and a
> good FTL would be able to 'hide' most of
> the details.

Here we have to agree to disagree. My experience with JFFS2 suggests
that while it can "deal" with NAND, it doesn't do so very well.

I also don't believe that a single FTL works well to cover the range
of differences between NOR and NAND. I'd rather have a separate FTL
for each, that concentrates on doing a good job for that kind of
flash.