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Subject: Re: Regarding UBI scalability
From: Artem Bityutskiy <dedekind@infradead.org>
To: Corentin Chary <corentin.chary@gmail.com>
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Date: Wed, 04 Feb 2009 09:45:51 +0200
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On Tue, 2009-02-03 at 12:13 +0100, Corentin Chary wrote:
> On Tue, Feb 3, 2009 at 11:46 AM, Artem Bityutskiy
> <dedekind@infradead.org> wrote:
> > On Tue, 2009-02-03 at 00:44 +0100, Corentin Chary wrote:
> >> I was wondering how it is possible to get atomic operations using such tables ?
> >> The first thing that come to my mind is TFAT (two tables, one for
> >> operation in progress,
> >> the other considered as always "valid"). But I'm not sure it' the good
> >> way to do such a thing.
> >
> > Journal + commit mechanisms should allow doing this.
> 
> I'm asking some other questions, because in UFFS we are working on
> something like that, but not for UBI2. But if I can help for UBI2,
> I'll.
> 
> A journal node, would probably take less than 16 B. With min_io_size
> >= 512 B (sometime 2KB), a journal for map/unmap operation will take
> some time before being written.

Well, to guarantee integrity, I do not see any other solution but doing
2x2KiB writes on 2KiB-page NAND: start update (1), (write the LEB
somewhere), end update (2), (erase the old PEB). That's the price you
pay.

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)