[WBEL-users] Raid

[Kirby C. Bohling]

On Mon, Oct 18, 2004 at 05:17:25PM +0100, Conor Wynne wrote:
> > 	About the only thing I don't do that you describe, is I never
> > use cp to move that kind of data.  I always end up using tar or
> > rsync, but that's just an old habit I learned from the O'Reilly
> > Backup Book (tar can be used over a pipe, which means you can move
> > from machine A to machine B via SSH the same way you move data on a
> > local machine, so I don't have to worry about odd limitations of
> > scp).  Knowing one reliable way to move data locally and remotely is
> > easier for me.
> >
> > $ tar cf - /path/to/cp | ssh user@machine "cd /dest/path/ && tar xvpf -"
> > $ tar cf - /path/to/cp | ( cd /dest/path/ && tar xvpf - )
> 
> I would use rsync for this purpose, its what it was designed for - init?

	I'm confused what "- init" means in this sentence.

	I'm not attempting to sync two sets of data that are nearly the
same.  I use rsync, if over 50% of the data transferred is already
there and I just want to keep them in sync on a regular basis.
That's the situation I think of rsync is designed for.

	I've seen rsync got thru some incompatibility issues that no one
can every seem to explain.  At one point kernel.org finally just
posted a note that said if you are using the version 2.5.X of rsync,
it might fail mysteriously don't complain, get 2.5.Y[1].  I've seen
rsync leave processes lingering around days and days later that
never died without rebooting or manually killing them when run in
daemon mode.  I use it when it is the right tool for the job.  I use
rsync to create multiple backups around my network of important
files in an automated fashion, but I never use it to move my one
good copy of data around.

	rsync isn't necessarily on every machine, and it's yet another
set of flags to remember and syntax to remember.  I've never seen a
UNIX-like box that didn't have "tar" on it[2].  I've seen plenty of
machines without rsync.  

	I can use tar to move partitions, backup data to a file, move
data from one machine to another without an intermediate copy,  do
only updates, or check that the contents of the tarball match the
contents of the filesystem.  If it involves a filesystem, you can
probably get GNU tar to do whatever it is you want done.  

	Kirby

[1] http://lists.samba.org/archive/rsync/2002-May/002448.html - this
seems to reference the problem.  I might have the version numbers
wrong.  It's been removed from the kernel.org site, but I ran into
it a couple of times.

[2] If QNX 4.2 counts as a UNIX like machine, I've seen one that
doesn't come with "tar" or "gzip", it uses "pax" and "freeze"
instead if I remember correctly.