rsync and ditto

They are similar, but ditto is more comparable to a hybrid cp/tar utility. In earlier releases, ditto was nice because it was one of only a few utilities that preserved resource forks, extended attributes, etc. rsync later had this added.

rsync is nice since it's a standard utility and can be used on pretty much any platform you want, and creates backups in a non-proprietary way (i.e. you can get at your target data easily using other utilities). Not that Time Machine is overly proprietary in terms of the format it uses to write data, but there are unique ways in which it does its work. You might not have all the flexibility with your target data as you would with rsync data. Plus, Time Machine requires all Mac systems, whereas rsync gives you the flexibility of copying your data to pretty much any network device.

It just depends on what you may want to do with your data, and perhaps how locked in you want to be to a particular system. I personally don't mind being all or mostly Mac bound. That said, I don't use Time Machine -- I use SuperDuper for my backups...

homeshire wrote:
thanks for your reply glsmith. so you wouldn't have any problem recommending their use as a secondary backup or archive solution?

Nope, they're both fine utilities to use IMO. If you were copying data over a network, then rsync is better choice. Locally, ditto is fine. There are lots of ways to make local backups, these are just two. But they're free and easy, so that's something...

I have an external hd dedicated to time machine, still I worry about catastrophic scenarios, and would like another solution that would allow me to physically remove my backups to another space.

I have multiple backup targets for this reason, and use several for some of my data that I consider irreplaceable. Again, there's a lot of different ways you can go when thinking about data preservation (backup to a network device running a RAID, backup to multiple different targets, use local backups and send your stuff into a cloud somewhere (Amazon S3, .Mac, ...), burn DVDs, write to tape, etc.). I'm sure you'll find a variety of opinions in this and other forums on these topics.

But to get started, using some standard utilities to copy data elsewhere is a fine plan...

I would agree with your assessment of local versus network backup. Rsync does lend itself to performing backups and synchronizations across the internet at large. I have some homegrown shell scripts on three computers that are executed as launchd jobs which run during my commute to/from work and at bedtime, that ensure that my AddressBook, Safari bookmarks, Microsoft Office templates, and iCal events, are kept in sync with one another across the three "clients" (home desktop, work desktop, and roaming (travel) laptop) with the "master copies" stored on a fourth "serving" machine. Rsync has an option switch to tunnel it through secure shell (ssh), which is how I use it, so the remote connections are encrypted, and with passwordless public/private keypair authentication in ssh, it lends itself well to autonomous file sync operations. Additionally, if you are syncing large amounts of data, by default rsync does incremental backups versus whole-file transfer (which can be done instead if desired).

I don't know whether ditto lends itself well to autonomous operations or not, or to encapsulating ditto transfers inside ssh or not, or to incremental backups. I've never used ditto like any of those scenarios.

I've not used Time Machine, either; but I thought that it was more or less for same-subnet types of backups (like to a local NAS) and don't know whether it can have a secure shell wrapper put around it for long-haul backups or not. I don't know if TM does bootable clones of hard drives or not, either. For local backups, I currently use CarbonCopyCloner to maintain a bootable copy on a second internal hard drive.

I find that rsync 3.0 is better at preserving metadata. (2.6 is included with OS X 10.5.7, so if you want to use rsync 3.0, go to http://www.samba.org/rsync/).

If you use 3.0, be sure to apply the fileflags.diff and crtimes.diff patches.

See http://www.bombich.com/mactips/rsync.html and http://www.bombich.com/mactips/image.html for more info (Carbon Copy Cloner uses rsync 3.0)