How do I save my iPhone backup files to my Airport Time Capsule?

Create a folder in the Finder, choose Make Alias from the File menu, then Go to Folder from the Go menu, provide ~/Library/Application Support/MobileSync/ as the path, rename Backup to Backup_old if needed, rename the alias to Backup, and put it into the MobileSync folder.

(152301)

It would be necessary for you to move your complete iTunes library to the Time Capsule drive.

Personally if your Time Capsule is being used to store the Time Machine backup, I strongly recommend against doing that. Storage of data on the same drive that Time Machine uses for its backup is a known method to corrupt your Time Machine backups.

Create an alias or symbolic link to the desired location and put it at ~/Library/Application Support/MobileSync/Backup/, moving or renaming the existing folder if needed. This folder isn't part of the iTunes library, and can be moved independently of it.

(152300)

If you are using Time Machine to back up your Mac, the backups of your iPhone are also automatically copied over to the Time Capsule inside of iTunes.

In other words, your iPhone backs up to iTunes on your Mac. Then, when your Mac backs up to the Time Capsule, all of the iPhone backups in iTunes are also backed up along with the other files on your Mac.

From the original message:

I do not want my iPhone/iPad back-ups taking up space on my MacBook Air hard drive

Transferring them through Time Machine won't reliably do this; they'd be deleted from the backup drive in time. While it's better to use a regular external drive instead of the Time Capsule for them, the method I posted above still applies.

Basically, this thread is about moving the working copies of the backup files, not backing them up.

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The Time Capsule was designed for your backups, specifically using Time Machine on a Mac. While you can place other types of files on the Time Capsule drive, it does not work all that well in my experience.

Keep in mind that if the only copy of a file is on the Time Capsule.....and the Time Capsule disk has a problem.....you will lose that data since you have no backup. For example, we've seen a number of users who make the mistake of moving their iPhoto or Photo Library to the Time Capsule to try to save space on their Mac. Same for the iTunes Media Library.

So, the only copy of the image library or media library is on the Time Capsule....with no backup in the event of a Time Capsule drive problem.

It is much simpler, faster and more reliable to use a USB drive connected directly to your Mac to move over data that you don't want on your Mac, then Time Machine can back up both your Mac and USB drive, so you always have a backup in the event of a problem.

The whole idea behind making a Time Machine backup of your Mac is if the hard drive fails on the Mac.....(it will, it's just a matter of when and not if)......you can replace the drive on the Mac and reload the backup from Time Machine, so your Mac will look just like your "old" Mac, with a minimum of effort involved.

But, it's your call. Good luck on your decision.