Samsung EVO Data Recovery

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lcoughey
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Joined: Thu Jan 08, 2015 7:23 pm

Samsung EVO Data Recovery

Post by lcoughey » Mon Dec 07, 2015 5:28 pm

Based on the date stickers from other labs, we are working on a Samsung 840 EVO SSD that has been offline for almost a year. We have been able to image the drive, but not without a huge amount of read errors. I will write a more detailed blog about this issue later, but thought it might be worth sharing sooner than later.

1. Samsung is using TLC NAND chips in these SSD drives (in layman's terms, squeeze as much as you can from the NAND to make it as cheap as possible)
2. This NAND has huge issues with losing charge if not accessed for periods of time, resulting in more errors and slow reads because of the increased need for ECC calculations to read
3. Samsung's fix for this "slow read" issue is a firmware patch that instructs the drive to continuously rewrite data back to the drive, keeping it fresh
4. If powered off for any period of time, the firmware patch will not help and data will start to fade away.

We are seeing this in the current recovery project which should have only been a firmware issue, but is now a much larger mess. From what I've seen thus far, we will be lucky to get 25% of the files recovered without any unreadable sectors in the file.

We recently just purchased 3 of these drives, of which we have 2 in circulation. I'm giving serious consideration to pulling the 2 from productivity.

lcoughey
Site Admin
Posts: 341
Joined: Thu Jan 08, 2015 7:23 pm

Re: Samsung EVO Data Recovery

Post by lcoughey » Tue Dec 08, 2015 1:44 pm

To further the current case, here are some stats:

4% of the drive has unreadable sectors
Only 7% of the files are not affected by bad sectors
100% of the zero filled unused sectors read without any errors

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