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Erasing solid state drives (SSDs)

#1Mr HangmanPosted 8/23/2014 6:47:19 AM
I noticed a topic from a couple days ago that looked good, but was closed. I thought I'd reply anyway.

http://www.gamefaqs.com/boards/916373-pc/69885018

Solid state memory, whether it's SSD hard drives or USB flash drives, use a storage medium called NAND flash. When these memory cells are written to, it causes a small amount of damage to it. After re-writing data to the cells ~10,000 times, it becomes unusable.

To deal with this problem, these devices have their own processor embedded in them which tries to write to every cell evenly. This causes the entire drive to wear out at a more equal rate, so it lasts as long as possible. If it didn't do this, then frequently modified parts would burn out and then your drive would effectively be shrinking. This is called wear-leveling, and it's completely hidden from the operating system. The drive doesn't tell you what it's doing even if you ask it, it just silently remaps portions of the drive all the time.

This is a problem if you want to erase a file and be really sure that no one ever gets it back. Some people know that when you erase a file, the operating system usually does not overwrite it (it just marks the space as being free) so it's still there for a while, but with SSDs you can't even try to overwrite it and be sure it was the same place thanks to the wear leveling. If for some reason an intelligence agency or a professional data recovery company got a hold of your SSD, they could disassemble it and read the data manually, finding things that appeared to have been deleted.

SSD secure erase programs work with the drive and tell it to re-flash every cell, ignoring the wear leveling. This way you can be really sure all the data is gone. That will add a small amount of wear to the drive, but given their size and how many times they can be rewritten, it's very unlikely that anyone will burn it out without trying.

Of course most people don't need to worry about that, since they probably don't have any reasonable expectation that any adversary capable of this kind of forensics would take their drives. And if you do, you should be using some kind of full disk encryption, so that it won't matter what they find, and maybe switch back to magnetic drives, too.
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#2cuteboi100Posted 8/23/2014 7:38:11 AM
Good to know. The wear on the drive is something frequently mentioned but to put it into perspective it needs to be compared with HDDs.
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#3GTRagnarokPosted 8/23/2014 11:50:02 AM
Doesn't TRIM, which pretty much every SSD uses, make this a non-issue? With TRIM enabled, files are actually deleted from the NAND instead of just being marked as free space. It improves performance in the long term, but makes deleted files unrecoverable.
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#4returnofbeansPosted 8/23/2014 12:00:51 PM
improves performance in the long run? i dont have a SSD but when i do, i'm gonna be sure to ask more about that. sounds like something every one would like not just for those who wish for privacy.
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#5GTRagnarokPosted 8/23/2014 12:11:09 PM
returnofbeans posted...
improves performance in the long run? i dont have a SSD but when i do, i'm gonna be sure to ask more about that. sounds like something every one would like not just for those who wish for privacy.

I guess it's better to say that TRIM helps to prevent performance from degrading over time. Windows 7 and 8 has automatically enabled it with every SSD I've used, so you shouldn't worry about turning it on.
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#6AsucaHayashiPosted 8/23/2014 12:12:38 PM
SSD secure erase programs work with the drive and tell it to re-flash every cell, ignoring the wear leveling.

got examples of such a program? preferably decent and free.
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#7PhilOnDezPosted 8/23/2014 12:13:05 PM
Without TRIM deleting a file basically works the same as with an HDD, the system doesn't actually do anything to the file, it just removes it from the cache and marks the space as free. Before that space can be rewritten to it needs to be cleared and then it can accept a new bit. This allows you to recover files but slows down how fast it can be written to. With TRIM the drive preemptively clears the files to allow them to be immediately written to.
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#8Mr Hangman(Topic Creator)Posted 8/23/2014 12:18:26 PM
The secure erasing programs are often vendor-specific. I have a Samsung drive, and they provide one to work with their drive.
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What senses do we lack that we cannot see and cannot hear another world all around us? -Dune
#9Orestes417Posted 8/23/2014 12:19:01 PM
That's because the actual function is part of the drive firmware
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#10AsucaHayashiPosted 8/23/2014 12:43:35 PM
Mr Hangman posted...
The secure erasing programs are often vendor-specific. I have a Samsung drive, and they provide one to work with their drive.


i have a samsung too.. so where do i find the program?
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PC hardware doesn't need to match console hardware in price when PC gamers save literal thousands from the software they buy.
http://i.imgur.com/9Yv0R2Z.jpg