Secure erase questions. 10.7.4

I just did a 7 pass secure erase on an external hard drive. I have two questions about it.

How do I know that a 7 pass secure erase was actually performed? Is there a way to determine this?
and
I am getting ready to do another 7 pass on my internal HD and I noticed this:

"secure erase overwrites data accessible to Mac OS x. Certain types of media may retain data that disk utility cannot erase."
What "media" or data is that?

Using 10.7.4

TIA
John

I suppose the way to determine that the 7-pass happened really is to send the external drive to a data recovery house and have them try to recover your data (an expensive venture), or just plug the drive into someone else's computer and see if anything is visible/accessible.

The warning message from Disk Utility is basically addressing situations where you have devices that have memory that is hidden from OS X, like a backup or shadow thing. This is not common with consumer HDD's, so you need not worry about it..

A 7 pass erase takes ages, that's how you'll notice its been done

a 3 pass would do to be honest

As for data, even a 7 pass erase will not delete everything. Some fragments of data can be left at the edges of the disk track. But only worry about that if you are on the FBI most wanted list. Getting at that sort of data recovery requires

a) A lab
b) A team of technicians
c) Specialist equipment
d) A lot of time, and
e) Several thousand dollars

Unless your data fits that sort of time and expenditure, then dont worry

That sort of data recovery applies if you are:

a) A drug baron
b) If convicted you are kept away from the other inmates for your own safety
c) If convicted you get to go to a special facility on the island of Cuba

Thanks for the info

It is a 2tb drive w about 500gb free, used for a year or so, and it took nearly 24 hours so I guess that represents "ages."

and just in case...

If convicted you get to go to a special facility on the island of Cuba

Click to expand...

can you get netflix there and what is the password for the wifi?

Thanks again

John

Anything more than 3 passes is overkill.

It has been shown that the built in secure erase with HDerase tool on Windows makes data irrecoverable.

It should be no different for Mac.

If that doesn't ease your mind put a few hollow point rounds into your Hard Drive.

yes, the comments have eased my mind and answered my questions, thanks. Somewhere it says that the 3 pass is good enough for the dept of energy, whereas the 7 pass is good enough for the DoD.