Format a Solid State Drive
From Mac Guides
When selling a Mac, it is a good idea to wipe your old data off of the hard drive to prevent the buyer from accessing personal information. A quick format in Disk Utility, however, will still leave some data behind, so people started wiping the disk by writing random or pseudorandom data to the disk to cover up old files.
Some new Macs, such as the MacBook Air and Retina MacBook Pro come with Solid State Flash Memory that cannot be wiped in this manner because of hardware implementations. When wiping a flash-based Mac, the following steps should be used.
Steps to Wipe a Flash-Based Mac
Encrypting your drive
- Open System Preferences
- Click on Security & Privacy
- Click on the FileVault tab and click on "Turn On FileVault"
- Follow the prompts to enable FileVault
- Restart your computer and allow FileVault to encrypt your drive. This may take some time depending on the size of your disk.
Note: You may decide to skip all warnings about creating a recovery key and storing the key with Apple since you will be erasing the drive in the next step.
Format and Install Mac OS X
- Once FileVault has encrypted your drive, boot the computer into Recovery Mode by restarting and pressing Cmd+R
- Select Disk Utility from the list of options.
- Select your drive and select the "Erase" tab.
- Select "Mac OS Extended (Journaled)" from the "Format" List, then click "Erase..."
- Once the disk has been erased, exit Disk Utility and Select "Reinstall OS X" from the Recovery Utilities
How this works
By encrypting the drive first and then formatting, you are locking the door (encryption) and throwing away the key (reformatting) then bulldozing the building and building a completely new structure on top of it. Any old data will not be able to be recovered.