There are several reasons why backups can take forever on an iPhone, so here are a few tips you can try that should increase the speed of your iPhone backups and restores. Yes, these tips work on Mac OS and Windows, and for iPod Touch too.
Fix slow iPhone backups by deleting photos
If you have a large camera roll on your iPhone, you might be really slowing down your iPhone backups. This is because the iPhone backup process will copy all your pictures regardless of whether or not there have been any changes made to them. The solution?
Regularly backup your iPhone photo’s and then delete the originals from the iPhone.- Launch iPhoto (or Image Capture or whatever app you use to backup photos)
- Copy ALL images from your iPhone to your computer
- Ensure that you have backed up all your iPhone photos to the computer
- Delete ALL of the originals from the iPhone / iPod Touch
- Proceed to backup as usual through iTunes
Your backups should now go much faster. It is no coincidence that this tip is recommended by
Apple Support, because it works.
I’ll be the first to admit that I was skeptical of this solution until I tried it myself; I had 1,728 photos saved in my iPhone camera roll. After I backed them all up into iPhoto and deleted all the originals from the phone, my iPhone backups speed improved dramatically – I went from a painfully slow four hour backup process to a more reasonable 45 minutes with this tip alone.
Delete old and unused apps from your iPhone
If you aren’t using an old app anymore, delete it, there’s not much reason to keep it around on your iPhone anymore. Deleting these ancient apps can help to speed up your iPhone backups too, since there is less data to transfer at each backup or restore.
Remove unused media from the iPhone
Old apps aren’t the only thing that can slow down backups, so can media. We already discussed deleting photos from your iPhone and the big improvement that makes in backup speed, but deleting other media can help too. If you find yourself never listening to some ancient albums, or watching those old TV shows you copied over 8 months ago, just go ahead and delete them from the iPhone. Deleting video files seems to be particularly effective.
Regularly backup your iPhone
Allowing too much time to pass between backups can really increase the amount of time necessary to backup your iPhone. Try to
keep regular backups of your iPhone, just get in a habit of making one full backup once or twice a month. I have noticed a direct correlation between the length of time a backup takes to complete and how often I perform full backups: the longer time that passes between backups the slower the backup will be.
I’m trying to install iPhone OS 4 and the backup and install is really slow, help!
Many users are reporting very slow backup and install processes for updating their iPhone and iPod touch to iPhone OS 4. If you are experiencing this problem, I would highly recommend letting the backup and install run during a time you will not be using the phone for several hours, ideally overnight. Just start the iPhone OS 4.0 install and backup process and let it run while you sleep, you will wake up to the new OS4 being installed and you will have made a recent backup, which will speed up future backups and installations as well.
My iPhone backups are still extremely slow, help!
If you’ve tried all these methods and your iPhone backups are still extremely slow (and by extremely slow I mean well over a few hours, I’ve heard reports of up to 9 hours… yikes!) then you can try the last resort: Restore your iPhone to it’s original factory settings.
Remember that by doing this without a backup you will LOSE ALL DATA ON YOUR IPHONE including all media, music, apps, phone numbers, notes, everything, so be absolutely certain that you don’t mind restoring to factory default settings without a backup. This almost always resolves the slow backup problem, but if you don’t have anything to restore to then you will have a completely blank iPhone with nothing on it. There are some suggestions that restoring the iPhone is necessary when there has been a filesystem corruption, which can lead to extremely slow backup speeds and other strange behavior. Again, you will lose all your iPhone data so this is a last resort.
If you’ve looking for the location of your iPhone Backup files, then look no further. Whether you use Mac OS X or Windows, the iPhone backup process is basically the same, iTunes backs up all of your iPhone files and identifier information to a specific directory in the following locations… 
By default your iPhone will automatically sync and create a backup each time your iPhone is connected to your computer. If you want to manually create an iPhone backup though, it is very easy. 