Guess TLC isn't good for storage after all

hojnikb

Senior member
Sep 18, 2014
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So earlier this year i bought a cheap flash drive (8GB) with toshiba 15nm TLC flash and AlcorMicro AU6989SN-GTA flash controller. Curious to see how well it fares with read degradation, i've filled it up with h2wtest test data and ran a speed test. This was the result



After 48 days it looks something like this


Quite a drop there, eh ? It gets better. I did a test afterwards every couple of weeks and speed did indeed drop consistently. But funny thing happed the other day i was testing..



This was after roughly 7.5 months after i first wrote the test data on it. Corruption.
So yeah, this flash drive can't even follow the jedec spec, which supposedly assumes 1 year retention when p/e are exhausted.

If anyone is curious, this were the settings i used for the controller prior of writing the test data.


(there are lots of fun stuff you can do with MPtools and some can affect performance as well).

Anyone has similar findings ?
 
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C1

Platinum Member
Feb 21, 2008
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Now you know why I didnt mess around & buy the less expensive PNY SSD that uses TLC nand ( CS1311), but instead paid more & bought the CS 1322 that uses MLC nand.
 

hojnikb

Senior member
Sep 18, 2014
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91
Now you know why I didnt mess around & buy the less expensive PNY SSD that uses TLC nand ( CS1311), but instead paid more & bought the CS 1322 that uses MLC nand.
To be fair, SSDs usually use higher quality NAND and stronger ECC (ldpc) along with more overprovisioning. But still, something like this could might as well happed to an SSD, just probably not in such a short time frame.
 

Elixer

Lifer
May 7, 2002
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We have no idea of the quality of the NAND though, AFAIK, there is no way to check how good it is, except in a lab.
It would be nice if we had a more advanced Windows file system that could tell us about bitrot that is going on.
 

hojnikb

Senior member
Sep 18, 2014
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It is the worst long term storage option there is.
Its also the must susceptible to read degradation and possible curruption as demonstrated above. People usually don't leave them powered and i don't think those simple controllers do any rewriting of old data.
 
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nerp

Diamond Member
Dec 31, 2005
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Yes, flash drives are good for temporary file transfers and OS installs. I'd never use one for actual storage. That's what hard drives, redundant storage and cloud backup is for. :)
 
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FFFF

Member
Dec 20, 2015
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You really shouldn't compare flash drives with SSDs even if they use the same NAND storage since controllers are the biggest factor in performance and the ones used in flash drives are the most low-end ones.
 
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hojnikb

Senior member
Sep 18, 2014
562
45
91
You really shouldn't compare flash drives with SSDs even if they use the same NAND storage since controllers are the biggest factor in performance and the ones used in flash drives are the most low-end ones.
This is very true, but controllers can only compensate for the degradation so much before curruption occurs, especially if the drive is powered down.
 

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