Macbook Air 2010 SSD question

dpo said:

Given a MBA 2010 which I used without any particular precautions for about six months until the release of Lion, at which point I encrypted the drive using Filevault...

Can anyone indicate the likelihood that, if I sell it on, someone could retrieve data from the machine (from its pre-Filevault days). Thanks.

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Turning on FileVault 2 encryption under Lion, rewrites the whole disk. When you erase and reformat the disk to be unencrypted, nothing will be recoverable without the disk encryption key.

If you go to sell the Air, you would want to erase/reformat the disk and do a clean install of OS X using the recovery media that came with your Air. (You don't want to install Lion as you would have to enter your AppleID and password to do that.)

dpo said:

Right, but the issue is that for about six months I ran Snow Leopard with all my data essentially unencrypted on the SSD. I then installed Lion and encrypted the disk. Isn't it possible that there is some similar gotcha to FileVault encryption as with an SSD secure erase, in the sense that it doesn't actually encrypt every possible sector of the disk?

I guess the question is, in selling it on, how paranoid should I be that the Snow Leopard-era data is in some way recoverable?

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When enabling FileVault 2 on for your boot volume, it does encrypt every block on the disk as part of its initialization whether or not it's still in use by a file. This should take care of your data privacy needs.

It's not needed, but if you really want to be paranoid, fill up your SSD with random files then delete them. My suggestion would be to pick largish downloads like different OS X Combo updates. Different Linux distributions. For a traditional spinning disk, a single pass erase in Disk Utility would be enough.