from the manpage on my ubuntu development system..

 mke2fs is used to create an ext2/ext3 filesystem  (usually  in  a  disk
       partition).   device  is  the  special file corresponding to the device
       (e.g /dev/hdXX).  blocks-count is the number of blocks on  the  device.
       If  omitted,  mke2fs  automagically  figures  the file system size.  If
       called as mkfs.ext3 a journal is created as if the -j option was speci‐
       fied.

so it looks like -j is the default.  -J can be used to specify journaling size and or the device to journal on.

RIck



On Thu, Aug 27, 2009 at 12:59 AM, PerOlof Bengtsson <po@hemmamail.se> wrote:
Doesn't ext3 require the -j option when creating (eg. mkfs.ext3 -j /dev/sda1 ) the filesystem to turn journalling on?
/PO

PO Bengtsson

________________ Reply Header ________________
Subject:        Re: [Gumstix-users] mmc file corruption mitigation
Author: richard dorfner <rdorfner@gmail.com>
Date:           2009 August 26th 14:47

Ah, My bad then, I was assuming ext3 did NOT do journalling.  Also, ext3 is
what the instructions say to use to generate an mmc card image.  So now the
question is, how robust is ext3's journaling mechanism?  I was under the
impression that journalling would take care of the problem associated with
file system corruption when power goes away during a write. Is that not the
case though?

I've only very recently started to dig into the file systems and which to
use here at work with our current project. I've sort of been leaving that
for the end as I've been assuming that it won't impact how anything works,
overall, except for file integrity and the ability to recover with fsck.


Thanks,
Rick

jffs2 is designed to be used on raw NAND (like the internal NAND
> memory that comes with the Overo). I don't think it will work on an
> MMC card. The MMC cards have their own internal wear leveling
> algorithims etc.
>
> You'd probably want to look at EXT3, which does journalling and could
> be used on an MMC card.
>
> There is a newer file system, called UBIFS, which we're just starting
> to look at at work, so I'm not sure if it's a candidate for MMC cards.
> I know that it's layered, and will definitely work on raw NAND.
>
> --
> Dave Hylands
> Shuswap, BC, Canada
> http://www.DaveHylands.com/
>
>
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Say you can or say you can't, either way you will be right.
Computers are like old testament gods: Lots of rules and no mercy.