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I recently sold my 128GB Crucial M4 SSD (I have a much larger capacity OCZ SSD, which is faster), and need to wipe the drive.

I know that the 'toughest' wipe that can be done is a 35 zero-write military-grade 'nuke', which essentially wipes the data on the drive 35 times over.

I wouldn't normally bother with this secure-erase, but the drive contained classified high-security software files of my own creation, and I really do not want anybody else to gain access to the information. There's rumors that just a single format will do it, but I've tested this and my drive-recovery software was able to find the files after the SSD was formatted.

No, I'm not going to destroy the actual SSD, since that'll be a waste of money, and the fact that I've already sold it for a fairly handsome price.

My question is, can a 35 zero-write wipe harm an SSD? I will continue researching on how to wipe my data completely (I know that formatting just recreates the partition table, and doesn't remove the actual files), but I'm curious whether the 35 zero-write will harm an SSD in any way.

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    If it is "classified high-security software" I suggest you smash the drive with a hammer and take the loss. There is no software out there which can't be reversed if the person knows what they're doing. – Matthew Williams May 18 '14 at 21:02
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    On a real HDD, a 35 zero-write wipe would be applied to each and every sector of the drive. Because of wear-leveling, that same type of "wiping" would be applied is some unknown fashion, and may not overwrite every Flash block. You should not use a technique for magnetic HDDs on electronic SSDs. – sawdust May 18 '14 at 21:47
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    If your information is really "classified high security" you should go and destroy the device physically since the data may be worth more than the hardware. – miho May 18 '14 at 22:17
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    Otherwise you could give an full erase a try, but it would enough to do it once on an SSD. 35-times is useless on an SSD. Your issue has been that you didn't have done it right. SSD are doing a lot of optimization internally, you may not be able to securely delete it that easy. – miho May 18 '14 at 22:20
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    @zyboxenterprises - Yes. What you want to do can damage a SSD. It will significantly decrease the lifespan of the drive. Additionally it won't do what you think it will do. Your senistive data more then likely will still be on the drive, The proper way to store data on a SSD is to use encryption this is because SSD have extra memory cells and we have no control where data is written to. This means you could wipe all the active cells but none of the inactive cells that previously stored your data. If you trust the manufacture use the built-in mechanic to wipe the drive. – Ramhound May 19 '14 at 0:13
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I've written an answer in the past on wiping drives. Its tangential to your question but there's no practical purpose in doing a 35 pass DOD wipe on a modern drive. The guttman method, which the DOD wipe is based on assumes you were wiping a drive with much bigger data domains than a modern drive, with unknown internal encoding.

As for damage, while 35 passes is quite a lot of writing, modern SSDs, even MLC and TLC drives quite happily handle thousands of cycles and terabytes of writes -There are many endurance tests floating around online such as this.While entirely pointless, this isn't likely to appreciatably reduce your drive's lifespan. What you really want to do is a sata secure erase - which tells the drive you want those sectors erased, and incidentally dosen't need 35 passes.

  • Accepted this as the answer (unaccepted the old accepted answer), no idea why I didn't mark this as the accepted answer in the first place. – AStopher Mar 16 '15 at 17:33
  • ssdendurance.com seems to be down. – Hashim Aziz Dec 24 '18 at 19:11
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If you have a Linux machine, what you can do is write /dev/zero to the entire drive, then /dev/random and then /dev/zero, and in that manner you would first write 0s to everything (actually deleting the files), then random 1s and 0s, and then deleting THAT again, and that is more likely than anything to render data incomprehensible.

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    This fails if the controller relocates the blocks. The old data could still be kept in its original location while the new data (0s, random etc) gets stored somewhere else. – Cristian Ciupitu May 18 '14 at 22:50
  • Not nearly, if you keep writing until the drive is full. – Aviator45003 May 19 '14 at 21:24
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    SSDs have a spare area which is not exposed to the user. For example "the S3700 has 264GiB of NAND on-board but only exposes 186GiB of it (200GB advertised capacity) as user accessible storage, the rest is used as spare area to improve performance, consistency and endurance." (from AnandTech). – Cristian Ciupitu May 19 '14 at 23:32
  • If only 186GiB of the 246GiB is exposed, wouldn't multiple passes eventually use all the space in a round-robin fashion? If the controller doesn't expose the rest, who's to say it can be found by even the best experts if they don't know what they're looking for? Unless you've got root credentials to the US DoD or a company like Google--or you're trying to hide your new algorithm that backdoors SHA256--is what you're hiding really sensitive enough to panic beyond a multipass wipe? Even the bad guys can't waste resources on small fish. (A quick format is nearly useless.) – durette Feb 18 '19 at 19:22
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There's no reason to think that "wiping" would harm the drive any more than any other normal writing of data to the drive. SSDs do have a limited life but the number of write cycles they will endure is in the millions, so 35 writes is insignificant.

The reason you could recover files after the 35 zero-writes is that it didn't write to the location where the files were saved. SSDs distribute the writes to new locations rather than the same location where the previous data lives. This is intended to keep the "wear" on the drive even. To properly erase an SSD, you must erase the entire drive including space the file system considers empty.

See this question for more details: SuperUser - permanently delete files from a flash drive.

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    He did just a "quick format". Not a full on Dod-35. That would have hit every block on the SSD, even the reserved space for wear-leveling. – Tonny May 18 '14 at 22:06
  • Where in his question does it say he only did a "quick format"? Whether he wrote to the entire drive or just tried to write over the specific files is unclear. What is clear is that some of the sectors containing his data were not overwritten. A single overwrite to the entire drive would have more than likely eliminated all the data. In any case, the question was whether he would damage the drive and the answer is no. – Dave Becker May 19 '14 at 5:19
  • @Tonny Actually, I DID do a quick format. – AStopher May 19 '14 at 6:44
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Actually, the best way of removing previous HDD/SDD (or whatever) data is getting the storage full. If you format the whole device and then you fill it with random data until there is no space left. There is no way someone could ever get to whatever data was before that. And you don't need any special tool for that.

  • There are still arguments as to whether data can be recovered after being over-written. Ref: blogs.computerworld.com/node/5687 , nber.org/sys-admin/overwritten-data-guttman.html . Also, it's not the 'Best' way ... The algorithm wipe is still known as the 'Best' way – Just Lucky Really May 18 '14 at 22:52
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    Have you read the articles you linked? They say that overwritten data can't be recovered. And that maybe it was possible with HDD in 1996. :) – drkblog May 18 '14 at 22:58
  • The relevant quote: "Since writing the above, I have noticed a comment attributed to Gutmann conceding that overwritten sectors on "modern" (post 2003?) drives can not be read by the techniques outlined in the 1996 paper, but he does not withdraw the overwrought claims of the paper with respect to older drives. " – Michael Frank May 18 '14 at 23:04
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    And here is the final line from the first link: "The notion that overwritten sectors can be recovered by searching for 'shadow' copies on today's hard drives is false." – drkblog May 18 '14 at 23:06
  • @drk.com.ar I can confirm that your method works, as data is listed as 'unrecoverable' when it is written over. – AStopher May 19 '14 at 7:37
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You only did a "Format Quick" which only re-writes the partition tables.
You didn't really wipe anything, except the partition table.

A regular normal format would have over-writen the entire filesystem.
Even then the wear-leveling mechanism will probably leave about 5 to 10% of the data intact in the "reserved space". (Depending on the size of the reserved area and the exact algorithm used by the drive.)
In theory someone could recover information from that. (Good luck trying. Nobody has yet been able to reliably demonstrate that ability as far as I know.)

A DoD short (3 passes) wipe with a tool like DBAN will exercise every sector of the SSD sufficiently that also the reserved space will be completely overwritten at least once.
For an SSD that means previous content is destroyed beyond recovery. (It's not like a harddisk where residual magnetic charge can remain on the platter, providing a faint "ghost" of the original value.)

This will not damage the SSD, it's just a bunch of writes, but you should not do it on the same SSD every day for an entire year.

By the way:
The 35 times overwrite "standard" was created in the 70's based on harddrive technology that was current at the time. Even then it was highly dubious if data was recoverable after more than 2 overwrites.
Since that time harddrive technology has come a long way. Density and complexity has gone up several orders of magnitude. And modern drives compress data as well.

To my knowledge nobody as ever been able to prove that any significant amount of data could be recovered after 3 writes. (At least not with public, verifiable, methods.)
IMHO: The NSA or some other spy-agency might have the means, but knowing what I do about harddrive and SSD technology I really don't think they stand a chance after 3 overwrites, regardless whether is a SSD of classic harddrive. On a classic harddrive they may get a few bytes here and there. On a SSD nothing.

Conclusion: A single pass wipe is good enough for 99.999% of all cases.
In your data is really valuable do a 3-pass DoD Short style wipe.
If you are really paranoid: Physically destroy the drive. Wanton destruction can be quite therapeutic :-)

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