Ext3 users - Apr 2002 - Raw EXT3 block format

Hello Guys,

I am looking to extend/create a file system that span networks/device of any
kind, shape and manner :) Check out http://www.insync.za.net/openufs/ (also
on http://openufs.sourceforge.net - but Iam not here to adv. the site !)

I would like to know, where can I find what EXT3 will write to the disk, how
it works etc.

Surely EXT3 will write something like this :

Block 0 - (1024 bytes) {DATA}
Block 1 - (1024 bytes) {FAT type block}

Hope this makes sense.....

Cheers,

Pieter De Wit

On Apr 03, 2002  17:16 +0200, Pieter De Wit wrote:
> I am looking to extend/create a file system that span networks/device of
any
> kind, shape and manner :) Check out http://www.insync.za.net/openufs/ (also
> on http://openufs.sourceforge.net - but I am not here to adv. the site !)
First note - UFS is a really bad name for this project, because this is
commonly used for "Unix File System", which is used by Sun, HP, BSD,
etc
as their primary filesystem.  Linux even has a driver for this (see fs/ufs).
> I would like to know, where can I find what EXT3 will write to the disk,
> how it works etc.
> 
> Surely EXT3 will write something like this :
> 
> Block 0 - (1024 bytes) {DATA}
> Block 1 - (1024 bytes) {FAT type block}
This data is described in many places on the net (a good starting point
would be Ted's http://e2fsprogs.sourceforge.net/ site, which has links
to such documentation).  The ext3 filesystem has exactly the same
on-disk layout as ext2 does.  It looks like you have a background with
MSDOS/FAT filesystems?
> Hope this makes sense.....
Yes, this is actually a very interesting project.  In fact, I'm part
of a team working on a distributed ext3 implementation right now
(see http://www.lustre.org/ for details).

Not to be overly negative, but it would seem that if you do not even
know how ext3 stores its data on disk, it would seem a very difficult
challenge to write a distributed ext3 implementation.  If you are
really interested in working on something like this, I'd consider
downloading the Lustre code and seeing how it works first.  We have
"Lustre Lite" partly working already, which distributes metadata and
data storage across servers, along with the beginnings of a lock manager.

If you are still interested, you may consider contributing to Lustre -
it is fully Open Source (GPL) software.

Cheers, Andreas
--
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert

On Wed, Apr 03, 2002 at 05:16:22PM +0200, Pieter De Wit
wrote:
> Hello Guys,
> 
> I am looking to extend/create a file system that span networks/device of
any
> kind, shape and manner :) Check out http://www.insync.za.net/openufs/ (also
> on http://openufs.sourceforge.net - but Iam not here to adv. the site !)
> 
> I would like to know, where can I find what EXT3 will write to the disk,
how
> it works etc.
> 
> Surely EXT3 will write something like this :
> 
> Block 0 - (1024 bytes) {DATA}
> Block 1 - (1024 bytes) {FAT type block}
> 
> Hope this makes sense.....
> 
> Cheers,
> 
> Pieter De Wit
You can find the ext2 format detailed on
http://www.freesoftware.fsf.org/ext2-doc/

The current ext3 code, the one included in the 2.5.x kernels, is
basically ext2 + journaling, so the format on disk is pretty much
similar.

I had a peek in Mr. Tytso's ext3 notes and there was something about an
"inode V2" format, but other than that, I haven't seen any trace
that
things would be done differently than in Ext2.

Hope this helps,
EKS - Dave Poirier