[SOLVED] Repair a Crucial 250GB SSD

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Rocky Bennett
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Re: [SOLVED] Repair a Crucial 250GB SSD

Post by Rocky Bennett »

senjoz wrote:
Thu Aug 13, 2020 2:43 pm
My understanding of secure erase of SSD disks (or overwriting whole disk with whatever numbers) is that it uses one program/erase count. Program/erase endurance of SSD disks depends on flash type. Years ago it was said that SLC flash can endure 10000 program/erase operations, MLC 3000 and TLC 1000. Nowadays mainstream SSDs use 3D TLC and QLC flash chips and things may be different.

Regards,
Jože


Yes, that may be true but the SSD that I have overwritten with zeros on multiple occasions is a 7 year old Crucial SSD. I am sorry, I did not know any better. I resolve to throw that darn SSD away next time I do a clean install.
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Kadaitcha Man
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Re: [SOLVED] Repair a Crucial 250GB SSD

Post by Kadaitcha Man »

Rocky Bennett wrote:
Thu Aug 13, 2020 8:06 pm
Yes, that may be true but the SSD that I have overwritten with zeros on multiple occasions is a 7 year old Crucial SSD. I am sorry, I did not know any better. I resolve to throw that darn SSD away next time I do a clean install.
When you do that you are filling up every cell with data. Unbeknownst to many, in an SSD, 0 is 1 and 1 is 0, which is the exact opposite of a HDD, so if you're going to pointlessly fill every block, fill it with 1s. As to why it's pointless, fstrim causes the SSD to, wait for it, wait for it, fill every formerly used block with 1s. Data on an SSD is unrecoverable after a trim operation, so filling the SSD with anything is pointless, and filling it with 0s is deleterious, and that applies even if you did get lucky overwriting "with zeros on multiple occasions is a 7 year old Crucial SSD".
It's pronounced kad-eye-cha, not kada-itcha.
Lert
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Re: [SOLVED] Repair a Crucial 250GB SSD

Post by Lert »

I have very little idea on how SSDs actually work but I doubt that a 1 or a 0 is 'something' or 'nothing' or the reverse. I think that a 1 is 'something' and a 0 is 'something else'. The problem with having 'nothing' is a problem of sensitivity to outside influences such as distant thunderstorms, passing gravitational waves or even the wireless mouse dongle in an adjacent slot..
Petermint
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Re: [SOLVED] Repair a Crucial 250GB SSD

Post by Petermint »

SSDs first erase to zeroes (or ones depending on the memory and controller.) then write ones to the bits that are not zeroes.

SLC SSDs store 0 or 1 in one cell. MLC stores 0, 1, 2, or 3 in one cell. TLD stores 0, 1, 2, 3, 4, 5, 6, or 7 in one cell. QLD stores 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 11, 12, 13, 14, or 15 in each cell. They all erase to zero first.

The erase takes more time and power than the write. Trim tells the controller where it can perform the erase. The controller marks the empty blocks in an index. The controller can erase whenever it feels like doing some work, which might depend on other activity.

The erase might be a 4K block or something bigger, depending on the memory and controller. The SSD might have 8 memory chips but the controller might have only 4 memory access lanes, resulting in slower everything. This is why there are so many brands a few dollars apart and why benchmarks can be almost meaningless when they do not match your usage.

That 7 year old SSD would be good as a lower use device, perhaps the storage you use to copy files from one machine to another. I have 6 year old heavily used SSDs that are still a long way from their advertised maximum writes. I demoted them only because they are slow when used for writing 100 GB.
Rocky Bennett
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Re: [SOLVED] Repair a Crucial 250GB SSD

Post by Rocky Bennett »

Kadaitcha Man wrote:
Thu Aug 13, 2020 8:34 pm
Rocky Bennett wrote:
Thu Aug 13, 2020 8:06 pm
Yes, that may be true but the SSD that I have overwritten with zeros on multiple occasions is a 7 year old Crucial SSD. I am sorry, I did not know any better. I resolve to throw that darn SSD away next time I do a clean install.
When you do that you are filling up every cell with data. Unbeknownst to many, in an SSD, 0 is 1 and 1 is 0, which is the exact opposite of a HDD, so if you're going to pointlessly fill every block, fill it with 1s. As to why it's pointless, fstrim causes the SSD to, wait for it, wait for it, fill every formerly used block with 1s. Data on an SSD is unrecoverable after a trim operation, so filling the SSD with anything is pointless, and filling it with 0s is deleterious, and that applies even if you did get lucky overwriting "with zeros on multiple occasions is a 7 year old Crucial SSD".


Yes, I found all that a few years ago so I have not done this practice in a few years. But thanks for the reminder.
senjoz
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Re: [SOLVED] Repair a Crucial 250GB SSD

Post by senjoz »

senjoz wrote:
Thu Aug 13, 2020 10:42 am
But, the problem with SSD disks in external USB enclosures can be trim support. Many controllers in external USB enclosures do not support trim.
A few messages earlier I mentioned a problem regarding lack of support of trim operations in many external USB enclosures. Nobody commented on that. Have you any experience with that?

Regards,
Jože

EDIT: Maybe I sould open new topic regarding this problem.
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