11 September 2011

One of the nice things about SSD technology is that if it supports the ATA erase command, you are pretty much guaranteed to have pulled all the data off your disk, even in those “hard to reach” spots. This is really good news for a lot of people as SSD prices are dropping, they are finding themselves with small SSD disks that they’d like to sell.

With a standard HDD doing a secure erase amounts to writing data across the platter as many times as paranoia requires. Some do this 35 times, some do it 50 times and finally some people just write zeros to the disk and call it a day. On a big disk, such an erase can take hours for every single pass.

SSD can complete the erase in just a couple of minutes. From the people I’ve spoken to who work with data recovery, as far as SSD erase is concerned, once it’s gone, it’s really gone. Like with the TRIM command, you need to accept that this is a one way street.

Now you can’t erase your hard disk when doing a normal Lion install because it requires a Snow Leopard install to kick it off (it’s a download from the App Store). However I picked up an official Apple OSX Lion USB key so that I could do everything from scratch. As far as I know, this official key is no different from the one you can make yourself, so save yourself some cash by making your own….

Anyway after booting with the Lion key, I went to erase the disk and discovered that Apple has disabled all the secure erase features. So you can’t even write multiple times to the disk (which honestly is a good thing because it really wouldn’t help much and would actually just wear out your drive). In other words, even at this late stage, Lion does not support the ERASE command sigh.

Fortunately you can still erase your disk using good old Ubuntu and hdparm. There’s lots of tutorials on this floating around and I have found that closing the lid on the Mac and waking it up again is enough to unlock the drive. You just need to find a version of Linux that doesn’t crash when you close the lid. I found for example that Ubuntu 10.04 works great for my Macbook Pro, but 10.10 does not. Fedora gets a graphical interface but doesn’t come out of suspend… so you might have to play around with that a bit… You can find a tutorial here:

http://forums.macrumors.com/showthread.php?t=841182



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