data recovery in 10.3

n2nrn

I'm confused about data recovery in OSX

The two stories I've been told are:



1. The people at Prosoft who make Data Rescue X say that Unix immediately overwrites the file and therefore their recovery of trashed files is impossible, even if the machine was immediately turned off.



2. Mac Help says: Even after emptying the trash, deleted files may still be recovered by using special data-recovery software. To delete files so that they cannot be recovered, choose Finder > Secure Empty Trash. Files deleted in this way are completely overwritten by meaningless data. This may take some time, depending on the size of the file. You may want to use Secure Empty Trash if you sell or give away your computer. Are they referring to software like Prosoft Data Recycler?



So who's got it right? I have had requests to retrieve files that have been trashed, so the ability to do so would be a good thing to know. Thanks in advance for your help on this subject.



n2nrn

costique

Deleted files are not necessarily instantly overwritten. It depends on the size and number of deleted files, on the amount of free drive space and on what the running apps are doing. It's a kind of lottery. Due to the complicated and rather diverse nature of processes which you are running, it's absolutely unpredictable. In short, there is no guarantee that files you deleted a second ago are not overwritten yet, and there's no guarantee that files you deleted a year ago are already overwritten.