When you add an SSD to your Mac, it may be wise to separate the operating system from your personal data (home folder). The iTunes library and movies folder can better be placed on the normal hard disk because the super fast SSD often doesn’t have a lot of available space.
At the moment that you start re-installing your Mac again, you can simple separate the home folder from the operating system by following this tutorial. However, make sure that you complete these steps immediately after the installation of OS X is completed to prevent data loss.
Let’s get started by install your Mac like you are used to. After the installation is completed, copy your home folder in the root of the hard disk that you want to use as your data storage drive, don’t forget to enter the root password of your Mac.
Now open > System Preferences > Users & Groups > and click on the lock to access all the options.
Press the ctrl-button, and click on your username and select ‘advanced options’. In the new window click on the location ‘Home directory’ and choose the location of the home directory that you’ve just copied to your other hard disk. The ‘Home directory’ will now display the right path to the new home directory.
All of the images, movies, music, and documents that are being saved on your Mac will now be copied to the home folder on your hard disk. You can test if everything has gone correctly by opening iTunes and check where the iTunes content is now stored.
If you’ve double-checked that everything is working like it should, you can remove the home folder from your SSD.
Users are advised to create an additional user with administrator rights ( > System Preferences > Users and Groups). If the second drive for whatever reason is longer available, it remains possible to login to your Mac with this optional account. When there is no user available with a corresponding home folder on your SSD, you will not be able to login to your Mac.