Q: I have an iPhone 3GS and I want to know if there is a way to back up my sync info (contacts, calendars, etc) to an external flash drive. The last update wiped out all my stuff and now that I have most of it back I want to make sure it doesn’t happen again.
A: Unfortunately there is no way to do this directly from your iPhone without jailbreaking it and using third-party utilities. However, it shouldn’t be necessary to do this, as iTunes will normally perform a full backup of your iPhone each time you synchronize with your computer. This backup includes everything on your device except for media content that you would have originally synced from iTunes, such as music, movies, TV shows, photos, iBooks, and so forth; iTunes does not backup this information as it would make your backups considerably larger and it’s reasonable to assume that you can simply restore this information from your iTunes library in the same way that you originally synced it onto your device in the first place.
Note that iTunes normally only keeps a single backup of your device, and it will overwrite this backup each time you sync, so you will only get the latest information. An additional backup is saved whenever you perform an iOS upgrade just for an additional safety margin, but otherwise you only have the most recent backup available. You can see the backups stored by iTunes by going into your iTunes preferences and checking the Devices screen.
The backups themselves are stored in your ~/Library/Application Support/MobileSync/Backup folder on Mac OS X, in your home folder’s Application DataApple ComputerMobileSyncBackup on Windows XP or AppDataRoamingApple ComputerMobileSyncBackup on Windows Vista and Windows 7. You can backup these folders manually in the same way as any other set of files if you want to ensure that you keep a copy of your backups somewhere outside of iTunes, either somewhere else on your hard drive or on an external flash drive.
If you’re running iOS 5 and have setup iCloud, you can instead use iCloud to backup your device online. You will not have as much flexibility in terms of keeping extra backups, but it can be useful for ensuring that your iPhone is more frequently backed up without having to worry about plugging it into your computer on a regular basis.
If you’re syncing your contact and calendar information to a desktop application such as Windows Address Book, Windows Contacts or Outlook, you can also backup that information from there using the normal tools available for those applications. This can be useful in addition to the full backups made by iTunes or iCloud as it becomes simpler to recover individual information rather than having to restore an entire iOS backup.