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

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Message-ID: <47F30FDD.5080003@yandex.ru>
Date:	Wed, 02 Apr 2008 07:47:25 +0300
From:	Artem Bityutskiy <dedekind@...dex.ru>
To:	Willy Tarreau <w@....eu>
CC:	"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <andi@...stfloor.org>,
	Tomasz Chmielewski <mangoo@...g.org>,
	LKML <linux-kernel@...r.kernel.org>, penberg@...helsinki.fi,
	Jörn Engel <joern@...fs.org>,
	ext-adrian.hunter@...ia.com, jwboyer@...il.com
Subject: Re: UBIFS vs Logfs (was [RFC PATCH] UBIFS - new flash file system)

Willy Tarreau wrote:
>> Well, even auto-levelling storage should benefit from a filesystem which 
>> minimizes the total number of flash sectors churned, which means doing 
>> as few writes as possible and to large, contiguous sections.
> 
> Exactly. At exosec, we ship one appliance which writes statistics to a
> partition on a compactflash every 5 minutes. We preferred to go with JFFS2
> exactly because of this reason. We never had any problem proceeding this way.
> I'm not sure if it would have been the same with ext2 though.
>

Yes, as I agreed in a previous mail this may make sense in some cases.

But in general it is not a good approach. Basically, it is wastage of resources.
Indeed, first the firmware on MMC/SD/etc makes efforts to make flash look
like a block device. It gives you in-place updates, but by cost of performance
and reliability. Then you just drop this nice property, and use JFFS2, which
assumes it has only out-of-place updates. But if this solves the task you have
- fine!

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)
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