I was using a sparsebundle to backup my OSX drive on an always-mounted external drive. I did that because I (mistakenly) thought that would prevent the OS from seeing the extra OS.) Well, I just learned that if the drive the sparsebundle is on is a mounted drive, then the OS sees the sparsebundle as “mounted”, too. (Actually it sees it as just another folder.)
So, there I was, using a sparsebundle to backup my boot drive, thinking that it would separate the backup from the main OS drive.
It does not. I noticed that 1Password was forever warning me about the presence of a second copy of the app when I tried to update. I complained in their forum, only to learn of my ignorance. You may not see that sparsebundle as available, but the OS sees it as just another folder! So, to the OS, it does indeed look like I have two copies of 1Password… and two copies of everything else as well.
I didn’t know that until this morning, and I’m glad I found out. I have switched to a sparseimage instead, and that cures the problem, although my software has to explicitly mount the image before copying to it (and dismount it when done.)
So, if you think that you’re hiding anything in a sparsebundle from the OS… you’re not.