Selling my early 2011 MBP with 128GB SSD. I used disk utility to erase the Mac HD but it took only a few seconds. How can I be sure the SSD was "erased"?

That's all it takes to do a fast erase. What were you trying to do? Your SSD has been erased.

To erase a disk all that is necessary is to erase the directory. Since the directory is usually small that can be accomplished very rapidly.

Zeroing an SSD can be done, but it involves a lot of writing and reading. It should not be done very often because every time one does it, it will shorten the life of the SSD a bit. However, if you have data on the SSD that you don't wish to be found by anyone, then you can do this:

1. Open Disk Utility from the installer's Utilities menu.

2. After DU loads select the SSD volume (usually Macintosh HD) from the

left side list. Click on the Erase tab in the DU main window.

3. Set the format type to Mac OS Extended (Journaled.) Click on

the Security button and set the Zero Data option to one-pass. Click on

the Erase button and wait until the process has completed.

4. Quit DU.

Now this will take a little longer (not hours) to do a one-pass Zero Data, but it will ensure none of your data can be seen or restored by others.

If your friend knows how, it is very likely your data can be retrieved using basic software recovery applications. It's been quite some time since I've used Snow Leopard. Help me out. Did you first boot from the installer DVD or did you look by opening Disk Utility from your startup volume? The Security button should normally become active after you configure the Erase options. Did you click on the Erase tab in Disk Utility's main window? I may not have explained everything thoroughly assuming you were familiar with Disk Utility.

You are aware, I hope, that you need to completely erase the drive then install the version of OS X that came with the computer originally leaving it with the Setup Assistant at requesting a language. There you should shutdown the computer. See the following but ignore the steps 1-2 because you've already done that part.

Clean Install of Snow Leopard

1. Boot the computer using the Snow Leopard Installer Disc or the Disc 1 that came

with your computer. Insert the disc into the optical drive and restart the computer.

After the chime press and hold down the "C" key. Release the key when you see

a small spinning gear appear below the dark gray Apple logo.

2. After the installer loads select your language and click on the Continue

button. When the menu bar appears select Disk Utility from the Utilities menu.

After DU loads select the hard drive entry from the left side list (mfgr.'s ID and drive

size.) Click on the Partition tab in the DU main window. Set the number of

partitions to one (1) from the Partitions drop down menu, click on Options button

and select GUID, click on OK, then set the format type to MacOS Extended

(Journaled, if supported), then click on the Apply button.

3. When the formatting has completed quit DU and return to the installer. Proceed

with the OS X installation and follow the directions included with the installer.

4. When the installation has completed your computer will Restart into the Setup

Assistant. After you finish Setup Assistant will complete the installation after which

you will be running a fresh install of OS X. You can now begin the update process

by opening Software Update and installing all recommended updates to bring your

installation current.

5. If you are planning to sell or give your computer away, then do the following:

After you reformat your hard drive and reinstall OS X, the computer restarts to a

Welcome screen and asks you to choose a country or region. If you want to leave

the Mac in an out-of-box state, don't continue with the setup of your system. Instead,

press Command-Q to shut down the Mac. When the new owner turns on the Mac,

the Setup Assistant will guide them through the setup process.

A very interesting article on ways to erase an SSD without destroying it.

http://www.macworld.com/article/2906499/mac-911-how-to-erase-your-macs-hard-driv e-the-right-way.html

Selling old Mac (4) Apple support

You are welcome.