ADATA Releases QLC SSD

OmniDyne

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ADATA released the dram-less 'Ultimate SU630' with 64-layer 3D QLC and is priced at $33 for the 240GB SKU. Comes with a 2-year/ 50 TBW warranty. Interesting, considering the Crucial DRAM-less BX500 comes with a 3-year/80 TBW and 64-layer 3D TLC.

At $33, this drive just isn't worth the price and should be avoided, especially for OS use. The larger drives share the same fate, avoid them as well.

For $30, one could purchase the 240GB Team Group L5 Lite 3D and receive closer to 200 TBW (thanks to the DRAM buffer) and a 3-year warranty.

I would avoid purchasing the SU630 in all sizes, especially in the current market. It's not priced well at all, has abysmal endurance, and there are far superior options.
 

OmniDyne

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QLC should just be avoided anyways.
The problem is ADATA doesn't make it obvious the SU630 uses QLC.

In the current market QLC SSDs should absolutely be avoided due to pricing, but I don't think this will be an issue as the technology improves and yields increase. QLC isn't quite as bad as one would expect, especially if you look at the reviews of the 660p. On paper, QLC is expected to be rated above 1,000 P/E cycles, which is similar to what 32-layer TLC is rated at, however, a good controller and good techniques can increase endurance quite a bit past this, especially if a DRAM buffer is used. Of course the SU630 doesn't utilize external DRAM so durability could be a concern and the 2-year warranty seems to reflect this.

Performance wise, experiencing QLC speeds can be completely avoided. The 660p uses a static SLC cache and a massive dynamic SLC cache pool (as large as 280GB) so speed definitely isn't an issue at the consumer level.
 

Intel_man

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QLC also has a problem with data retention. The higher density, greater number of levels, and smaller the process would promote an increase in charge leakage. There's a lot of variables in play when determining how long that takes before serious corruption of your drive can be experienced.


Note: This is for ssds (of all sorts, including but not limited to ssds using SLC, MLC, QLC, etc...) that are placed into storage and are not connected to a power source.
 

OmniDyne

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QLC also has a problem with data retention. The higher density, greater number of levels, and smaller the process would promote an increase in charge leakage. There's a lot of variables in play when determining how long that takes before serious corruption of your drive can be experienced.


Note: This is for ssds (of all sorts, including but not limited to ssds using SLC, MLC, QLC, etc...) that are placed into storage and are not connected to a power source.

How much worse is QLC flash about this?
 

OmniDyne

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That's after the flash has been fully exhausted though, right? As in the flash has met or exceeded P/E cycles? As long as the flash hasn't been fully exhausted data should be retained for years without power, even in a QLC drive I'd assume.
 
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Intel_man

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According to the whitepaper, the rated time for data retention is based on fulfilling the P/E cycles.
As long as the flash hasn't been fully exhausted data should be retained for years without power, even in a QLC drive I'd assume.
That depends on the QLC flash itself, temperature of storage, etc... The exact date is difficult to determine without a more in depth study on this matter. However, what can be said though is that QLC flash performs worse than the other flash types out there (SLC, MLC, TLC). There has been mentions about data retention back when MLC and TLC were introduced when comparing to SLC, but it never has been a topic of worry until QLC.
 

OmniDyne

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This article on the matter is interesting.

https://www.google.com/amp/s/www.pcworld.com/article/2925173/debunked-your-ssd-wont-lose-data-if-left-unplugged-after-all.amp.html

There has been mentions about data retention back when MLC and TLC were introduced when comparing to SLC, but it never has been a topic of worry until QLC.
This has always been a problem though. The Samsung 840 EVO had the retention charge leakage issue that required more ECC. Micron's 384-Gbit 32-layer 3D TLC flash is especially susceptible to interference; so much so that it took several firmware revisions to the controller to tame it. An appropriate controller, revisions and better LDPC, larger SLC caches, and overall larger capacities (note that the Intel 660p and Crucial P1 don't come in anything smaller than 500GB and the Samsung QVO QLC drives don't come in anything below 1TB) should alleviate any of those concerns at the consumer level.
 
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