[tlug] Data rewrite technology

["Lyle (Hiroshi) Saxon" <ronfaxon@example.com>]

I have a question that ties in with hard disk security and reliability - 
or the balance between the two.  I don't know if it's still the case for 
certain, but with the DOS file system, when you erased a file, it didn't 
actually delete the whole thing, but only the first part of it, and then 
the space occupied by the "deleted" file was marked as empty and 
eventually would get overwritten with new data.  From a security 
standpoint it was (is?) dangerous, as with the right software you can 
cull amazing amounts of "deleted" data off of drives.  But - there would 
seem to be two advantages to doing it that way - higher speed (since the 
bulk of the data isn't actually deleted, it is nearly instantaneous) and 
better longevity (the number of times the same magnetic medium can be 
written and written is not infinite).  I bring this up, as I just 
deleted two 60MB files on a flash memory card and it took quite a long 
while (compared to W2K anyway).  When deleting in Linux, is the 
operation basically what some software refers to as "shredding"?  
Certainly this is no pressing issue - I'm just trying to better 
understand exactly how things are working.