Hi ,
I need some help with the way CC works, but in return, I might be able to clarify about the way the solid state memory works?
Firstly does anyone know if CC wipes unused space on SS Memories by first filling the spare space with garbage, and then deleting it?
I ask because after several hours, I cannot find any up to date info on this? This is the ONLY way to "erase" anything from solid state memories.
The way SSDs work is different as you know to HDDs. HDDs have real memory addresses - So an address will ALWAYS point to a specific point on a specific track. SSDs have software built right into them at the chip level. It is called "Wear Leveling" and it's only job is to try to make sure that no memory address gets written to so much that it wears out long before it should. So memory address "x" might refer to position x+1 next time, and something completely different the next time and so on.
So no file can be "erased" on SSDs, as the wear leveling will be sending the writes to all different parts of the device and the original file will only be deleted and most likely still recoverable.
The same comes into play with MFT and also cluster tips. Say you have 4K clusters set up. When that is overwritten with a full 4K, then the old data is gone. But what if only a little data was written to it? The rest of that 4K might be marked as unused, but the old data will still be in there. These are the cluster tips, and while not likely to contain much, could in theory at least contain passwords, medical test results, confidential financial details or whatever. So some people like to clean them as well. They cannot be cleaned on SSDs for the same reason that files cannot be.
The MFT is kind of like a "Contents List" of what is on the drive and where it is located. On SSDs it also gets deleted when files are erased, but the wear leveling means it will not be overwritten for some time, potentially never overwritten. This is most likely if the drive was becoming full and it was written near the end of the MFT. If things are deleted and a lot less fo the drive is used, then there can be a lot in the MFT that does not get overwritten for some time.
Defragging an SSD is pointless. The drive reads data from wherever it is at the same speed as if the data was all in one continuous lump. Even if you try, wear leveling will mean the data gets moved to less used parts of the device and most likely even more split up. This will make no difference to the speed of the device, but leaves even more spaces with your potentially embarrassing old data in.
With SSDs, even a single overwrite means the data is gone for good. On HDDs there used to be "remainance". This was where the new track would not quite follow the old one, so an oscilloscope could often read the remaining magnetism in the old track and recover the data that way. This was why there were standards for how often a disc should be overwritten - You had to overwrite so often, that the slight wobbles from perfectly circular tracks would statistically most like have overwritten the position of the original track at some stage. I even wrote my own standard where every byte was overwritten by first binary 10101010, then 01010101. That way every bit was flipped ever 2 overwrites and the rest of the overwrites was to try and make sure the natural wobble would most likely have overwritten the original track at some point. Nice history, but not really relevant anymore. Modern high density HDDs have the tracks so close to each other that I have not heard of any data being recovered from being overwritten this way for many years. The tracks are so close, that the wobble has to be barely measurable and so the magnetic domains are so small, that nothing statistical remains after being overwritten AFAIK.
Sanitizing a drive for recycling or junking is another matter. Both SSDs and HDDs over time develop "bad sectors". The chips on the drive mark it as bad and not to be used. But the data that was written on it will still most likely be on it. If it is important that you do not want to take chances with even this data, then you can use Darik's Boot And Nuke (DBAN). I think there are other programs as well that claim to do the same thing, but are not as well known. Personally I always do a search for the manufacturer of the drive and the words "low level format". This is because ordinary erasing software like CC or even Eraser do not clean sectors that are marked as bad, and it is complicated by translation software. I don't want to get into that as it is horribly complicated...but basically drives have so much memory now that one of the chips on the drive has to translate the head/cylinder/track that the computer talks, to the actual head/cylinder/track of the HDD, or memory address of the SDD. So I always low level format those drives for recycling.
If a drive has failed and so cannot be sold, you can't sanitize it either... Now what? I have read some wonderful ideas, like blasting them with shotguns (TL;DR: Works with SDDs, not so much with HDDs, - Too much of the surface remains undamaged). Also not everyone has shotguns, thermite, or neighbors that will not freak out. So SDDs can be destroyed by electrically destroying chips. A taser does a reasonable job, or earth one of the thicker tracks and attack the rest of the tracks with the guts of an air ionizer, neon lamp driver or any other high voltage. BE SAFE - BE INSULATED AND PHYSICAL PROTECTION AS CHIPS CAN AND DO EXPLODE IF YOU PUT TOO MUCH CURRENT THROUGH THEM. If you do not know how to be safe, then physically destroy them by taking out the boards and cutting them with "tinsnips" right through the middle of each chip, so that you can see the thin sliver of dark, glassy silicon in the middle of the chip has been cut through. Use good scissors on the chips in old "smart cards" like in decoders, some travel cards, and "chip and pin" credit cards. HDDs can have the discs taken out and melted under a torch if you have one, or the red hot embers of a dying big bonfire. You can also scour off the surface with wire wool / Brillo pad. Better is an angle grinder with a "flap disc" or just a plain sanding disk, or even a palm sander. Just use "emery cloth" instead of sandpaper. I am not sure, but you might even be able to remove a sufficient depth these days with nothing more than a polish with Brasso or similar.
I wrote this because I needed help primarily, but also because while searching for the answer (not just on the CC forum, but the internet in general), I found there was a lot of confusion and sometimes incorrect advice. I thought I might be able to pay something forward?
Regards to all.
S.