[NCLUG] Server-to-Server backups

[DJ Eshelman]

Hey all...

So I have an interesting project coming up soon - we've recently deployed a
Debian server hosted at ServerBeach (for web hosting) - we're looking at
adding a mail server with archiving (likely CentOS if I get my way with
it).  Since the mail server will require backups for compliance reasons,
we've configured both servers with dual hard drives, the second of which is
sitting untouched as of yet.

Ideally we'd like to configure the servers to just simply backup their hard
drives to the other server's second drive - we figure that would be a good
level of redundant ability.  This is all easy enough, I suppose, but there's
one little catch:  We're limited in bandwidth to about 2000GB per month.
Now, I know what you're saying - what is the big deal?  That's a lot of
bandwidth!  But aside from the bandwidth we'd also not like this process to
consume a horribly long amount of time.

So, I've never done anything like this before - most backups I've ever done
have either been a mirror to a drive internally, a tarball to another drive
or your standard tape backup...

The question is this can we do a image backup across servers at the bit
level?  That way, only the changed bits would be backed up.  This is the way
that Windows DFS works and the speed has suprised me.  Surely we can do the
same or better!.  I know there should be a way to do incremental backups,
and if I have no other choice, it's what I'll end up doing... but surely
there's a way!  As of yet I'm not even sure how to start searching for
this.  My attempts thus far have been more frustrating than anything else.

thanks all!

-DJ