Acronis Drive Cleaner - Unneccesary wipe options?
I hope an easy question.
Could someone just clarify why it is neccessary to do 3 or more passes when wiping with Acronis Drive Cleanser (or any other similar software?)
I tried to explain the purpose of drive cleaner to someone else and I realised I did not understand the wiping process clearly enough myself!
MY PRESENT KNOWLEDGE IS SUMMARISED:
My understanding is that data is held on the hard drive by firstly magnetising a thin layer of suitable material on the platter to be 'low level formatted' to allow the controller to recognise each of the blocks.
It is then formatted again during the installation of the OS (e.g. XP) using the low level formatting as the reference point.
The OS then stores information on the drive by changing a 'character' or sector as a binary number i.e. an equivalent of 'FF in hex.'
MY POINT OF CONFUSION
Surely if each 'character' or sector is changed to something new, you cannot recover what was there before - because it has been changed.
Surely it is impossible to recover what was there before (using ANY utility?) because the binary '0''s and '1's have been changed and you can't reverse it.
So why repeat over-writing 'FF' in many passes?
Surely the very first time you change it it cannot be recovered.
I can understand disk recovery utilities which seek to find information on the drive which has not been over written with 'FF', but they cannot recover what has been changed by writing an FF 'over' it.
So. To summarise, why use many passes in Drive Cleanser. Surely once is enough? As you can tell, I'm not trying to be a cleverclogs or argumentative, I just don't understand clearly enough.
Can someone help please?