I understand some of what you're suggesting, but I'm a little confused on the Time Machine aspect. I use TM, but just in the basic sense. I actually don't know that much about it. You mentioned that it would recognize when I make a change or add something - then do you mean that it backs up the new version as a replacement of the old, or would I just have 2 versions then - the old and the new?
Also - I'm actually mostly concerned with my raw movie data and pictures from Iphoto in addition to Itunes. Would use use this method in the same way - keep all of these media types together on one external, and the computer stuff on another?
Old & New. For example, you render a 2GB movie, import it in iTunes, Tag it in iTunes (name, description, etc). When TM runs, it will back up that 2GB movie to your TM disc. Then, you notice a one-word misspelling in the description, so you fix it. TM will backup another 2GB version of the file. Then, you decide to drop an image into the part of iTunes in which a CD cover is typically stored (for example, using a movie poster for the movie). Again TM will backup another copy of the 2GB movie. So, now you've got the exact same movie file in iTunes, but your "fine detail" tweaks have resulted in TM allocating 6GB for it. That's pretty common with big movie files, so they will fill up just about any TM backup very quickly.
TM works like it should- which is good. It would be complicated to code TM so that it could know which copies to delete and which to keep.
That's why I've chosen to store big media files- like movies & tv shows & home movies on an external hard drive that is excluded from TM backups. TM will ignore that drive no matter what I do with updating files, fixing misspellings, changing "album" art, etc.
However, media needs to be backed up. So I use a separate external and Chronosync to take care of that. When I add a new movie to iTunes, I hook up the backup and run a Chornosync "sync" operation. The big difference is that Chornosync can be set up to only store the most recently updated version of the file. So in the above example, my 2GB (latest version) will be backed up as 2GB, not 6GB. If I notice another typo or something and update it, next time I run a Chronosync sync, the old backup will be deleted and the newly updated (again) version will replace it. Net backup 2GB.
This works well for your- and my- situation. I don't need TM for this kind of thing as I'm not constantly adding new content to the media drive. For example, I'm not constantly adding new email or address entries or calendar info, etc- all that SHOULD be backed up via TM. When I occasionally add new (big) media though, I know I've done it, and know to run a manual Chronosync backup.
At first, I was backing everything up on 1 external hard drive, but it has filled up very quickly. I may have been backing up too much. Do I need to continue to back up system stuff if nothing has changed? Or could I just back up the media as I add new to it?
If you're going to be working with lots of video, you need to be thinking about BIG storage. 1TB is probably not going to do it. I store my raw stuff on a 4TB WD external (also that same media drive). So, I've got all my big media for iTunes in one folder, and all my raw footage in another. Then, I've got a separate 4TB for Choronosync backups of that whole drive, as well as two 2TB drives for a secondary backup of each of the 2 folders (media & rawmovies). I also use Chronosync for the backups to the two 2 TB drives.
If I didn't have spare 2TB external drives already on hand, and I didn't already own those 4TB drives, what I would do now is probably buy one of the OWC Raid boxes like:
http://eshop.macsales.com/shop/hard-drives/RAID/Desktop/ and let RAID5 also act as my secondary backup. If I had the money, I might buy 2 of them, so that I could have a local RAID5 box hooked to my iMac, and then a separate one solely for backing up the first (and then storing offsite).
This might be something to consider if you have the money.
I'm pretty tech-capable, so I've also looked at something called unraid:
http://lime-technology.com/technology, which allows you to add storage as you need it, mix and match drives sizes & speeds, etc. So if I was completely starting over, I'd do that (but only because I probably have the tech experience to put one of those together and get it going). Once these external drives get nearly full, I'm probably going that way (unless something better shows up between now and then), as I can see the need for storage north of 8TB in the not too distant future (raw movie files really eat hard drive space), and I don't want to keep collecting individual external boxes. unraid has an interesting internal backup alternative to normal RAID. Instead of using some space on every drive, it uses one disc as a parity drive, which is a smart way to facilitate mixing & matching drive sizes. I like the concept as 3TB drives are just around the corner(s), so that solution can grow in capacity as bigger drives come out, without having to come up with something to do with the smaller capacity drives (RAID generally likes matched capacity & matched speeds). I also like the green nature of it (such as how as little as ONE drive could be spinning at any one time, compared to how RAID generally works). Etc.
In your case (I'm perceiving limited tech confidence from your post), that OWC solution may be the better way to go, or you could do more along the lines of what I'm doing now (with a couple of external drives).
I hope this is helpful. Ask more questions if anything is foggy.
