Time Machine allows you to backup multiple macs to one drive. You just plug it in, set it up, and you're good. If you look at the file system, you can see separate backups for both computers. At our home we currently do this with a Mac Mini and a MacBook. The Mac Mini is always plugged in, and the MacBook gets updated every couple weeks. We use a 1.5 TB drive from Western Digital. Given your description, I think this solution with your 2TB drive should work well for you.
The data backed up by both macs will not be the same, as no matter how hard you try, both computers will wind up having subtile differences, so the data won't be "exactly" the same. Backing up only one system doesn't seem ideal to me, but you can restore a MacBook from a Mac Mini backup. It works fine.
Also, you realize that the drive must be connected for you to access the photos and music that you have stored there. You'll have to factor that into your storage solution.
Your preferred setup is not possible: OS X can't share an NTFS disk with Windows for backup because Time Machine needs HFS+ (from http://support.apple.com/kb/HT1427):
Manually preparing a new disk for Time Machine
(...)
If you want to partition the disk, click the Partition tab and
select a layout. Make sure "Mac OS Extended (Journaled)" is selected
in the Format menu for the partition that will be used for backups.
Click Apply.
Luckily, you don't need two separate drives. Using partitioning you can trick your computer into thinking it is connected to more than one drive, although there's only one. In this case, two partitions will suffice, one HFS+ and one NTFS.
(Why only one NTFS partition although you back up 3 Windows computers? Because Windows stores backups in folders named after the computer name so there are no conflicts whatsoever (see this post). You can use one NTFS partition to store backups of multiple Windows computers.)
I'd recommend that you create the HFS+ partition on your Mac first, then, on your Windows computer, format the other partition to NTFS:
- Plug your drive into your Mac.
- Open Disk Utility (in Applications/Utilities).
- Select the drive and select the Partition tab.
- Create two partitions. Format the first partition as HFS+ (and give it a name like "Time Machine"). Leave the other partition as "Free Space". See here for more details.
- Eject the drive and plug it into your Windows computer.
- Format the second partition as NTFS.
When you're done, plug the drive again into every Mac/Windows computer and select the corresponding partition as backup drive (see here for OS X and here for Windows).
To prevent the NTFS partition from being mounted every time you connect the drive into your Mac add this entry to /etc/fstab (as explained here):
LABEL=BACKUP_WINDOWS none fusefs_txantfs noauto
Replace BACKUP_WINDOWS with the NTFS partition name.
This setup works like a charm.
I have a very similar configuration:
My external 1 TB drive, which I use for backing up my Mac and my wife's Windows PC, has two partitions called "Time Machine" and "BACKUP_WINDOWS":
Best Answer
I would suggest using Mac Drive by Mediafour: http://www.mediafour.com/products/macdrive
I've used their product for years and it has always been rock solid. I'd say at $49.99, it is reasonably priced too. And honestly, you may find a free solution, but to me, data integrity will always trump a slight to the wallet.
That is if you absolutely want one partition, but considering that one is a dedicated Time Machine repository, I would advise against it. While Time Machine makes a simple folder with all the backups (Backups.backupdb), it is ill-advised to store anything else on that particular partition. I know people that do it without problems, and all Apple says about the practice is the following:
But again, it's just good to keep things separate in my opinion. I'm not one for arbitrary compartmentalization, but in the case of backups, maybe letting them have their own room might not be such a bad thing.