linux-kernel - Re: UBIFS vs Logfs (was [RFC PATCH] UBIFS

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Message-ID: <20080401090309.GA7465@logfs.org>
Date:	Tue, 1 Apr 2008 11:03:09 +0200
From:	Jörn Engel <joern@...fs.org>
To:	Artem Bityutskiy <dedekind@...dex.ru>
Cc:	Tomasz Chmielewski <mangoo@...g.org>,
	LKML <linux-kernel@...r.kernel.org>, penberg@...helsinki.fi,
	ext-adrian.hunter@...ia.com, jwboyer@...il.com
Subject: Re: UBIFS vs Logfs (was [RFC PATCH] UBIFS - new flash file system)

On Tue, 1 April 2008 11:45:56 +0300, Artem Bityutskiy wrote:
> Tomasz Chmielewski wrote:
> >For me, the motivators to wait for LogFS are mainly the facts that it
> >can work on traditional block devices, and not only on pure flash:
> 
> Sorry Thomasz, for me this makes zero sense. There are _much_ better file
> systems for block devices. UBIFS may work on top of a block device as
> well (just needs few hacks to make it possible) - it is not a problem
> at all, it is just _senseless_.
> 
> JFFS2/UBIFS/LogFS is a separate _class_ of file-systems. The are designed
> for _flash_, which has completely different work model then block device.
> They are _native_ flash file systems.
> Here are more details: 
> http://www.linux-mtd.infradead.org/faq/general.html#L_mtd_vs_hdd
> 
> The traditional FSes _cannot_ work on top of flash. The solution for this
> is using FTL, which emulates a block device on top of flash. It _hides_ the
> real device, and fakes a block device for you. And you can use traditional
> FSes on top of that fake block device.
> 
> The whole _point_ of this separate class of FSes is because we believe
> we may do much _better_ job if we use flash _natively_, instead of using
> FTL. FTL is the place where you loose performance, reliability, and so on.
> 
> And you are saying about using a native flash FS on top of a block device
> like an SD card. This is just not sane: SD card first emulates a block 
> device
> for you, looses performance at this point, then you again emulate a flash
> on top of this, and suffer from this again.

About a year ago I would have used roughly the same argument.  But in
the meanwhile I have accepted the fact that any piece of flash I'll use
in a notebook in the next five years will likely use SATA or USB as a
transport medium.

Jörn

-- 
...one more straw can't possibly matter...
-- Kirby Bakken
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