I am trying to maintain muliple instances of time machine backups from a single Mac. What I am doing is maintaining separate storage hard disks (e.g., one for photos, one for videos, one for Aperture Vaults). I back each of these up to separate disks or disk partitions on other hard disks. I previously did this pretty simply with Retrospect, but they have basically dumped single-user support and I'm trying to move on.
Not knowing I "couldn't" do this, I created a Time Machine BU disk (Photo BU) to backup the photo storage by excluding the internal hard drive and having the Photo Storage and Photo BU drives attached. All went fine.
I then recorded the exclusions I'd used, changed the Time Machine BU disk to a different partition "Computer BU" (telling time machine to switch rather than share the disks), redid all the exclusions so that it was backing up the internal drive minus my Aperture Libraries, and performed another backup.
At this point I read somewhere that Time Machine will work with only one BU, and that it would just perform another full backup if I went back to update the Photo storage backup. I'd made some changes to the files in Photo Storage, so I again changed the Time Machine BU disk to be Photo BU, (switching rather than sharing), re-entered the exclusion info to match the original ones, and ran a backup. While it initially said there were no previous backups, it proceeded to change a few hundred megabytes of files (out of the 60 GB backup) and exited normally, showing the info for previous and most recent backups.
This seemed to work fine. My question is, will Time Machine crash and burn if I continue this, or is it an OK workaround even if more effort than desirable? Can anyone suggest improvements?
Pro, OS X Mountain Lion (10.8.2), various external HDs, Macs since the Mac 512 FatMac