copying large files between filesystems

[Andrew Scott]

Hello, this isn't necessarily a Fedora specific question either.  It is 
happening while operating from a Fedora Core II install, and I just 
subscribed to this mailing list which seems to get a good deal of 
talented traffic.  Please allow me to throw this one out there and I 
promise to be of assistance with other people's problems in the future.  :)

I'm trying to copy a large bzip2 archive that is a little bit larger 
than 2 Gigs, from a disk with a resierfs filesystem on it, to another 
disk with ext3 filesystem.  I only mention the filesystem types because 
I think this might be the cause of my problem.  Immediately after I made 
the original bzip2 archive I ran md5sum on the resulting file, and kept 
a copy of that number.  After I copy the file to another filesystem, I 
can not get the same md5sum.  I've tried cp, rsync, scp, and dd and they 
each seem to come up with different md5sums.  The byte count is the same 
however, but the md5sum is always different, so something however 
minimal is changing and henceforth throwing off the whole bzip2 archive 
and rendering it unexstractable.  I'm totally stressed because this is a 
back up of my homedir from before a reinstall.  :-/  And I'm worried 
that the original filesystem that I wrote the backup to (the reiserfs 
filesystem) was so old that it didn't recognize files greater than 2 
Gigs, silently.

If I md5sum the file, still in it's place, it's still good.

Any ideas why I can't get matching md5sums from a file copy between 
filesystems of different type?  Any ideas how to recover from this?

Thanks in advance, anyone, with thoughts,

-Andrew