[Leica] Seagate

[jbm at jbm.org (Jeff Moore)]

2009-07-31-19:04:23 Tina Manley:
> Country estate ;-) (rural farmhouse) and town home - about 25 miles 
> apart.  I would love to know how to synchronize them over the 
> internet!  We have very good bandwidth in both places.

Ah!  So...  they're close enough that I assume it's not a matter of
mothballing one or the other for the season and moving, you're probably
back and forth pretty often.  So the computer infrastructure could (and
maybe does) stay powered up both places.

First off, it'd be good to do a little back-of-the-envelope calculation
of how much data you're likely to add/change and need to synchronize
between locations at a time versus the available bandwidth.  It's
possible that copying to a disk and tossing it in the car is actually
faster.  The old-school way of putting this (which perhaps Brian might
be the only other here to remember) is "Don't underestimate the
bandwidth of a station wagon full of magtapes."

If the simplicity of schlepping a disk is for the best, maybe look into
a Firewire-800 drive.  Its connector (derived from something used in a
consumer video-game machine?) may be specified for more plug/unplug
cycles than the USB connector.

If you want to do magical 'net synching, I'd first look at using
rsync-over-ssh.  You'd set the firewall box(es) at the place(s) expected
to accept a connection from the other place, which would initiate the
transfer, to port-forward port 22 to a host with access to the part of
the disk you're updating, and set that host up to accept an ssh
connection and be able to fire up rsync.

Jeez, I wish you weren't on Windows.  I assume all of this is somehow
possible there, but I don't know any of the details.  It's pretty
straightforward on a "real" operating system (something Unix-flavored,
like Linux or, to a sufficient extent, Mac OS X).  (There are some
oddities synchronizing the more obscure metadata the Mac insists on
keeping, but synchronizing plain files works well.)

Anyhow, you could allow the source host to update your whole data tree
if necessary, but use a handy "backup" option which forbids overwriting
pre-existing files (to prevent screwups);  or you could do essentially
the networked version of your disk-in-the-car, keeping a transfer area
on disk as the only place which could be scribbled to.  This might be
safer, if less magically convenient.  If you did the "backup" flavor of
transfer, you'd need to prune out old files occasionally, after you'd
verified that their replacements were okay.

You'd definitely want someone computer-savvy to set this up, ensuring
that the ssh setup was secure and limited to the expected use, and that
rsync couldn't scribble where it shouldn't.  rsync and ssh are included
parts of Mac OS X and most Linux distributions, but I dunno if you have
to pick them up and install them on Windows.

 -J