From jonathan at stl.gathman.org  Sat Nov  3 00:03:56 2007
From: jonathan at stl.gathman.org (Jonathan Gathman)
Date: Fri, 2 Nov 2007 23:03:56 -0500
Subject: [Linux] Time Machine/Rsync
Message-ID: <0DF25814-13CC-4F77-AEC6-330852FC94E9@stl.gathman.org>

Hi Folks,
   Given my new Apple iMac, and the new Leopard O/S, some of you  
expressed interest in "Time Machine".  I suspected, and Stuart noted  
that it's implementation is a nice rendition of RSync.  I would have  
to say yes, though they currently only support an attached drive.  For  
those uninitiated, you should look into rsync, especially the ability  
to view whole system images at once but only spend disk space for  
changes due to the clever Unix ability of "Hard Links" (two directory  
entries pointing to the same file content).  The other cool thing is  
that Time Machine knows what to backup based on "System Events" or  
Journal entries... There's no searching the whole disk for "archive"  
bits set (which may be mistakenly unset anyway).

   Many in the community suspect that since this was yanked last  
minute from the final release, that there were issues in the "network  
drive" portion, and they'd rather it didn't cause issues.

   I happened to have my backup drive partitioned out Windows/Linux,  
and since I now use rsync to backup my windows box (via Cygwin) to my  
Raid on the server, I decided to overlay that Windows partition for  
Time Machine.

   I think what Apple adds is two fold.  One.

   Apple's theory is that everyone knows they need backups, but backup  
utilities have been so cumbersome, they don't happen very often.  My  
personal experience with Windows Backup, is at the very end of a long  
update, you get a message to "insert a floppy"... Of course, my laptop  
doesn't have a floppy drive.  There's a no win.  If you cancel (what I  
had to do eventually, because I couldn't insert a floppy), the whole  
backup was thrown away.  Isn't THAT user friendly.

   Therefore, Apple not only wanted to do backups that were efficient  
(i.e. not a whole tape every day), but also that the users might be  
able to visualize and understand what's going on.

   So on the first score, I must say that setting up "rsync" backups  
on my windows box, though satisfying at the end, was not the easiest  
exercise.  You've got to think through, and understand a number of  
parameters, and I'm not sure I have it all perfect yet.

   On the other hand, Time Machine, for simplicity's sake, just asks  
for a drive or partition not on the current drive.  Identify it, and  
life is easy.

   Second, the GUI for finding your backup files is actually uniquely  
cool of Apple.  You can include the backups in the "Spotlight" search  
engine.  The Visualization that Time Machine does isn't just cool  
looking, it informs the user that you're working on past data, and  
allows the user to easily picture the "images" of that file over  
time.  In other words, I think the very cool 3D graphics are not just  
eye candy, but have serious use in helping the user picture what's  
going on.

   Anyway, the speculation is that the network ability will come in a  
special release... And that's fine.  I've got my nice drive to work  
with in the meantime.

   Personally, I think this is a truly excellent feature that will  
change the behavior of Apple users to one of those who actually have  
backups like everyone knows they're supposed to.

Jonathan Gathman
jonathan at stl.gathman.org