Little help with rsync and Readynas Duo

Don't use SMB. I used to use the ReadyNAS rsync server with my old iMac on 10.5, and it worked pretty well. I'm not sure why people wouldn't recommend it. But I would not recommend using the old rsync client version that comes with Snow Leopard. Before you use rsync with any Mac (even locally) you need to make sure you've updated to a newer version and patched rsync to be compatible with HFS+ extended attributes. Luckily the instructions are not too hard to follow, check http://www.bombich.com/rsync.html out. I dug up the old command I used to use with 10.5, which I used to sync a local directory to the backup share on the ReadyNAS:

rsync -rltEX --delete --progress --protect-args --size-only --rsync-path="usr/local/bin/rsync --fake-super" /local/path/to/directory readynas::backup/

The --delete switch deletes any folders/files on the remote share which you've deleted in the local directory.
The --progress switch gives you a progress dialog.
I don't remember what --protect-args does :oops:
The --size-only switch disregards time stamp differences on both machines and only uses file size to determine whether things changed
The --rsync-path switch I was using because I never bothered to put the new rsync in my path. However, using --fake-super is important because it helps you store extended attributes you may not have been able to capture otherwise.

But I don't think I was able to capture all of the extended attributes for every file, which is why I eventually stopped using it. For some files, extended attributes aren't very important. But in some cases, they are critical. Every Mac OS revision seems to use extended attributes for more and more, so be sure to have rsync log errors and test to make sure those rsync'd files work right. Long story short - if you're really just using rsync as a backup, consider Time Machine. You can use the Time Machine Editor app to modify the default interval, which is what I do on my MacBook Pro.