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From: Matthieu CASTET <matthieu.castet@parrot.fr>
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To: Indrek Kruusa <indrek.kruusa@artecdesign.ee>
Subject: Re: jffs2 Erase Block Summary overhead
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Indrek Kruusa a écrit :
> Ühel kenal päeval (neljapäev 15 veebruar 2007 5:30 pm) kirjutas Matthieu 
> CASTET:
>> Hi,
>>
>> after doing some test on a 64MB nand flash, we see that only 50 MB can
>> be stored on the filesystem [1]. The extra 10 MB are taken by jffs2
>> summary. If we disable jffs2 sumary in the kernel, the 10MB become
>> available.
> 
> This is interesting. I have a Puppy Linux build within 52MB (ps 512B/ebs 16KB) 
> and sumtool grows it to 57MB.
> JFFS2/device with ps of 2048B/ebs 128KB has much much better compression level 
> and sum adds ca. 3-4% for this case.
Mine is a ps 512B/ebs 4KB.

> You can play with "dry" mkfs.jffs2 and different page;block sizes/file 
> counts/file types to get the whole picture.
I don't get the same result with image generated with mkfs.jffs2 and on
the fly written file :
- with mkfs.jffs2 + sumtool give me only 7 % overhead
- on the fly write give me 15 % overhead


Matthieu