Looking for overview pros/cons of using compressed/read-only DMG (for online backups)

[dnanian]

Other than the time, temporary space required, and fact that it can't be updated, there's no real downside to a read-only DMG.

But - you might want to consider a read/write sparse bundle instead. I'd expect Mozy to be able to back it up, including its inner 'band' files, and an updated bundle would likely be faster to back up than a whole new DMG.

Remember that if your external large FW 'archive' drive isn't backed up, well, all that stuff is vulnerable. And if you don't want to lose it, ever, it should be.