Differential backup recommendation?

[Reuben D. Budiardja]

Hi,
I am trying to come up with a modest, cheap, and simple backup system for some 
of our servers & workstations here. This will be basically a kind of 
home-grown thing, rather than spend the money for commercial backup system.

We have one server that's going to have a rather big storage space for this 
purpose (about 400 GB) with RAID. So here's my plan:
For every remote server / workstation (or a directory in the remote machine, 
eg /home), I want to create a :

1. Full backup on day 1 to the backup server.

2. Write the full backup to media (either CD-R or CD-RW or DVD-RW, haven't 
really decided yet), and leave the data in the drives in the backup server

3. Differential backup on day 2 to day 7

4. Remove lask week backup from Harddrive, then Goto 1.

For step 1 and 2, I can use something like rsync, or rsnapshot, or even 
mondo-rescue which will nicely create the ISO files for me directly for the 
remote machines that I backup. So the first two steps is not terribly hard.

Now for step 3, I don't know what to do, and can use some recommendation. Is 
there an open source utility out there that will do this differential backup? 
I am thinking about storing this differential backup in different directory 
everyday, like day0/, day1/, day2/ etc. I've googled, and only come up with:  
http://rdiff-backup.stanford.edu/
I'll try that, but I'm wondering if people here knows some other, or can 
recommend some other. 

The advantage of doing this is so that I can have one week versions of changes 
on the machine, and can go back to specific day during that week to restory. 
I know the disadvantage is to restore could be more difficult, and after a 
week, data cannot be recovered to specific day, but we're willing to live 
with that (what I have now is even worse because I only have mirror for 
backup, with incremental backup every day). So  our requirement is pretty 
simple. 

I know that some people here have been in this game for probably longer than I 
live :), so I can use advice or criticism for the plan. And as I said before, 
I also need a recommendation of a utility that can do differential backup.

ps: I've read, and skim over the book Unix Backup and Recovery (very nice book 
BTW), but unfortunately, unless I'm missing something, it does cover 
differential backup utility in depth (or at least the free/open-source one).


Thanks in advance for any help.
RDB
-- 
Reuben D. Budiardja
Department of Physics and Astronomy
The University of Tennessee, Knoxville, TN
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