[sjk]

Originally Posted by dnanian

I'm not even sure where to start here, I have to say!

Somewhere, anywhere, nowhere ...? Thanks for the ultra-quick response, which I've read you have a reputation for.

One of the problems of 'clone' type backup utilities -- of which SuperDuper! is one -- is that it becomes awkward to try to develop a backup strategy that allows full rollback with incremental update storage. In general, doing that kind of things requires a backup catalog and a non-simple-filesystem storage mechanism, and we've been trying to avoid that.

Understood.

Hope you can clarify a few details with this simple procedure:

1) Use "Backup - all files" script to create a bootable clone of the system volume to a backup volume.

* Since it's a bootable clone it must do root authentication but there's no mention of that in the manual.
* What's the advantage of using SuperDuper for this vs. the Restore capability of Disk Copy (on 10.3)?
* Are any cache files removed, similar to Carbon Copy Cloner?
* Are Finder comment fields preserved?

2) Use "Smart Update" option later to refresh copy of the system volume on a backup volume.

* I presume that's similar to using psync with Carbon Copy Cloner (which I've never done; I'm a bit suspicious of its integrity "under duress")?
* Can any any combination of directory hierarchies be candidates for Smart Update?

And all backups are started manually; no automated scheduling (yet)?

Yet, in my quest for trying to figure out how to do this simply, I did stumble on some discussion (in the mount docs) of union mounts. It seems to be that a union mount of an image over another image might allow clone backups to be done while actually generating a storable delta in a separate image. I haven't done a full-fledged investigation into this, but it was an intriguing idea. You might want to check it out.

I'd noticed support for union mounts in the man pages but hadn't considered using them in this context -- cool idea. I played with union mounts a bit to overlay local filesystems over a NFS-mounted /usr/local hierarchies on pre-Solaris versions of SunOS so I'm familiar with the concept. I'd be interested in what you discover and I might do a bit of tinkering, too. I've been trying to get more familiar with creating disk images, ensuring that owners, groups, permissions, etc. are accurately preserved.

SuperDuper! can certainly make and update images, and you can front-end this stuff with various hdiutil functions to mount, create, or whatever, but without doing this kind of trick you won't have incremental rollback.

Yep.

Seems that incremental (and differential) backups on OS X are intended more for heavy-duty (and pricier) utilities like Retrospect and BRU.

Of course, you could have a number of sparse images stored on an external or network drive, named things like "monday", "tuesday", etc, and Smart Update them; you could roll back as many days as you have storage for.

Another option, if you're thinking dump: rsyncx...

I don't see the correlation. Normally when using dump for backups the destination would be a single archive file whereas an rsync(x) destination would be a directory hierarchy. A dump|restore pipeline to another filesystem would be more like rsync(x), and cloning.

Anyway, just throwing some disorganized, rambling, I'm-on-a-slow-GPRS-connection-and-can't-research-much ideas out there.

I'm impressed.

Thanks again for the feedback and ideas.