Re: Adding snapshot capability to Linux

[Andreas Dilger <adilger@clusterfs.com>]

On Apr 22, 2002  13:41 -0400, Kent Borg wrote:
> On Mon, Apr 22, 2002 at 11:07:46AM -0600, Andreas Dilger wrote:
> > Please see:
> > http://www-mddsp.enel.ucalgary.ca/People/adilger/snapfs/
> > 
> > What you describe is exactly what snapfs does.  The Sourceforge project
> > is currently inactive, but the code itself is GPL and only needs some
> > polishing up and maintenance to be useful (probably also some work to
> > get it all OK under 2.4 again).
> 
> Very interesting.  Firing up google.com/linux I found a LWN story on
> snapfs from a year ago March: <http://lwn.net/2001/0308/kernel.php3>.
> Other than looking to me like it might not be bootable, this looks
> very much like something someone named Kent Borg was asking about a
> few days ago.

Actually, because ext2/ext3 is used as the underlying on-disk format,
you could probably boot from a snapfs filesystem if needed.  The on-disk
layout is designed such that the "current" version of the snapshot is
what you would always get (the snapshot data is hung off EAs on each
inode).  However, since you would then have the root filesystem mounted
as ext2/ext3 and not snapfs, you could not use the snapshot features.

Cheers, Andreas
--
Andreas Dilger
http://www-mddsp.enel.ucalgary.ca/People/adilger/
http://sourceforge.net/projects/ext2resize/