Samsung 840 EVO - how to easily lose your data forever

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Roman_TS
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Samsung 840 EVO - how to easily lose your data forever

Postby Roman_TS » 07.12.15, 17:41

Hello all!

Today, I will try to post here 3 small story-tales about Samsung 840 EVO :) Right now - they are the most problematic drives from the list of supported drives in PC-3000 SSD.

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1. Story number one. Recently I have my personal SSD drive based on 840 EVO. It was installed in my laptop and I can't say that I'm working with my notebook too often - just take it in my vacation and in business trip several times per year. I bought this SSD as upgrade for default HDD drive in my Clevo laptop in November 2014. In Summer 2015 I found that for some reason, the speed of reading and writing become very slow - by default it should be 300-500 Mb, but I found only 30-90 Mb\s for reading. I spoke with our ACE Lab developers and did you know what we found? Everything is very simple - NAND memory in Samsung 840 EVO is TLC based, and it is VERY VERY Bad. After some time when you write the data on memory, the charge inside NAND cells is flow away. The voltage inside cells become worse and worse, and finally - flow away forever. It means that if you will not use your 840 EVO drive for some time, you will find that your SSD is EMPTY.

Speed become very slow because controller required more time for fixing ECC errors which are appear in NAND memory chips.
If you will rewrite all capacity with some pattern or with user files, and will check the reading test, results will be awesome again - 300-500MB for reading, and Samsung promise on 840 EVO box package...

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2. Story number two. For our SSD trainings we bought 8 Samsung 840 EVO 120gb drives, and our developers help to broke them and emulate problems with FW. Before they broke our drives, they install OS on it, and copy some files - totaly around 60gb.
After 4 month, when a large group of students came in Rostov for SSD trainings, we tried to recover this drive during our practise. And do you know what I found? 3 from 8 drives loose ROOT catalogue, a lot of files become corrupted, and full recovery was impossible. Firstly I thought that it is a problem of algorithm, but after another 2 month during another trainings I get 5 drives from 8 which were not recoverable at 100%! Through RAW recovery it was still possible to get some of data, but folder structure and a huge part of data was damaged forever.

3. Story number three. In the beginning of 2015 one our customer from Israel send for us damaged Samsung 840 EVO on 1 tb. This drive was very interesting for us, and our Samsung developers team start work with it. They spend around 6 month for getting access to user data, and for decryption of FW - it helps us to add 840 EVO in PC-3000 SSD support list. But you know what? During this 6 month, charge inside cells in this drive was flow away too, and around 80% of data become corrupted. The same symptom - too much of uncorrectable errors. Very-very bad memory chips with very poor quality.


You ask me - are the guys from Samsung didn't know about that issue? Why they did not find the way to fix this bug?!
And I will answer - they release new FW, which make very simple thing - in background, when you working with your laptop or with PC, it just rewrite customer data again and again, again and gain by cycle, every time with the only goal - to keep the data and charges inside cells "fresh". When drive is not connected to power source, charge from cells is flowing away.

Of course this bug fix is not solve the main problem - bad quality of NAND memory. That's why after 840 EVO, Samsung decided to release new generation - Samsung 850 EVO\PRO and Samsung 950 for laptops - in new generations they cancelled TLC memory, and decided to use new 3DNand memory chips with better quality.


Starting from PC-3000 SSD 2.0.2 it become possible to recover data from Samsung 840 EVO drives.

When we working with Samsung 840 EVO and going to recover some data, you must be prepared for not perfect recovery result - a lot of data might be damaged! In future our developers will add read-retry feature for Samsung SSD, it will help us to read data with much more better result than before.
With best regards
ACELab technical support
ts.acelaboratory.com
blog.acelaboratory.com


lcoughey
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Re: Samsung 840 EVO - how to easily lose your data forever

Postby lcoughey » 10.12.15, 23:14

I just did a recovery that seems to be a victim of this issue. I suspect that the 3 months of sitting around awaiting the PC3K SSD update did not help. We were only able to recover about 7% of the files without read errors.

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Roman_TS
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Re: Samsung 840 EVO - how to easily lose your data forever

Postby Roman_TS » 11.12.15, 10:52

That's a pity... Say "Thanks" to Samsung company - they know how to apply Passive Security Erase :)))
With best regards
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lcoughey
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Re: Samsung 840 EVO - how to easily lose your data forever

Postby lcoughey » 14.12.15, 21:36

I feel horrible for all those unsuspecting users who might have bought one of theses drives for data archival purposes. Better hope that they never need the data again.


Pepe
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Re: Samsung 840 EVO - how to easily lose your data forever

Postby Pepe » 22.01.16, 23:47

it should get better publicity... let's keep hdd alive :)

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Roman_TS
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Re: Samsung 840 EVO - how to easily lose your data forever

Postby Roman_TS » 25.01.16, 09:59

Well, honesty as I know Samsung does not use TLC NAND after that incident. Now - only 3DVNAND, where the number of errors reduce in 10-15 times in compare with TLC :)
With best regards
ACELab technical support
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