Is QLC actually any more vulnerable to letting electrons escape than any other cell type? I'm not exactly a NAND architect, but how would reading/writing based on multiple levels of voltage have an effect on the ability to keep a charge?
If you wear out the cell, that's probably fair (and that happens faster in QLC for sure), but we're talking about WORM, so presumably that's less of an issue.
Probably worth bringing this up too if we're talking about data retention.
It doesn't have an effect on ability to keep charge. But if you double the number of charge levels and you are loosing charge at the same rate, you will get to the charge representing different level in half the time needed before.
So say I archived my files on a bunch of SSDs. Would I need to plug them into a power station or something every so often just to keep my archives intact? If so how often and long would that need to occur on your average SSD?
Pokemon Blue stored the save game in volatile memory (SRAM) and used a battery to keep it powered. Your save is still there because the sram has an extremely low power draw.
Read hot, store cold is the rule for SSDs. The hotter the environment they are in while they are active, the less wear and tear on the cells because it's easier to move the electrons around. The colder you store them, the harder it is for electrons to leak.
I generally wanted know how much of a bad idea that was, ignoring the cost, and how far away the industry is from having non-mechanical drives for storage purposes where some of us don't like mechanical drives very much.
Oh, and one thing I meant to mention were the transfer speeds and noise etc. After all of these years I'm very tired of the time spent, the noise and vibration.
The answer is, yes. The spec for P/E cycles is 1yr of storage persistence once that is reached. So if it is a 5k P/E drive, at 5k P/E cycles, the storage should persist for a year, before it wouldn't be retrievable. Of course that is only a very good chance of the data being recoverable without errors, not a perfect guarantee.
The lower the number of P/E cycles on the drive, the longer the data can be retrained error free. It isn't a log function and now I am too lazy to go pull up the white paper I had been reading on it for another Anandtech article I commented on recently. But an MLC drive they were looking at had something like 1/30-1/10th the raw read error rate of P/E count of 1 vs P/E count of 5,000 (I assume based on 2x nm flash drive, that was roughly the max rated P/E count for MLC).
So figure 10-20 years of data retention.
IF KEPT AT ROOM TEMPERATURE. NAND flash very rapidly loses charge at higher temperatures. At 70C, about what you could expect in a hot car on a sunny day with a black SSD enclosure with the sun right on it, it loses charge something like 300x faster. Even at 50C it accelerates data loss by something around 30-40x and 40C it is about 10-15x. This is all versus 20C storage.
So if you live in the tropics and leave SSDs laying around on a shelf in an unconditioned building, probably figure on a barely used drive you might get 1-2 years of data retention. On an abused drive, weeks. In the arctic you might get centuries of data retention.
won't leak faster, but it's a lot easier to tell the difference between 0 and 1 (SLC) than it is to tell the difference between 0110 and 0111 (QLC). That is to say you can leak a lot before 1 looks like 0, but don't have to leak nearly as much before 0111 looks like 0110
Endurance claims appear higher than normal and consumer availability is conveniently after the Company will be sold to the highest bidder
Anyone sampling these now should torture the crap out of them to see if the endurance claims are anywhere near accurate before this Company Vaporizes as fast as its claims
I'm all for QLC... for secondary storage only. Basically replacing a storage HDD used for media with a QLC SSD. Current TLC drives are far too expensive to replace multi-TB HDDs. Anyway, in that scenario QLC would be good enough, you're not going to be hammering the drive with writes.
For primary storage, a really good TLC based drive is a bare minimum. QLC, even supposed high endurance QLC, isn't good enough. Even if the endurance is truly as good as they claim, performance won't be. Especially when discussing PCIe-linked NVMe solutions (mostly M.2).
I envision a rig with an PCIe 4.0/5.0 main drive (possibly PCM/ReRAM), and a high-density QLC drive for mass storage.
Keep in mind, four bits is only 33% more than three bits. They immediately jumped to the idea of 100TB drives, but it looks like their upcoming QLC chips would support about 4TB. (Or 8 TB, maybe.)
I have a 3TB HDD for secondary storage. A 4TB would be plenty. :D Pricing, of course, is key. I don't anticipate being able to go all-solid-state for at least a couple of years.
For media you don't SSD at all, HDD's are plenty fast and responsive for it. Another thing is having a huge collection of images where you want to use the thumbnails often.
I'm not trusting QLC with my data. Some TLC are bad enough. Maybe for WORM storage but no way for daily use. They can lie about the 1000 P/E cycles all they want.
3D-QLC getting 1000 P/E cycles is not as improbable as it seems. Samsung's move to 3D-NAND brought an odd situation where the MLC based 840PRO had less endurance than the TLC based 850EVO. Intel / Micron didn't get this benefit as they chose to use floating gates instead of charge traps in their architecture. Samsung, SK Hynix, and Toshiba all use charge trap. If I recall correctly, the 1000 P/E cycles metric is where planer NAND ended up. It is conceivable that Toshiba was able to make a 3D-QLC NAND with equal endurance to its planer TLC predecessor similar to how Samsung achieved a 3D-TLC with greater endurance than its planer MLC predecessor.
However, I don't recall ever hearing 1000 P/E cycles used to describe the endurance of a 3D-TLC (charge-trap) NAND chip. An appropriate comparison point would be Toshiba's 3D-TLC vs Toshiba's 3D-QLC. That would help us to understand the true trade-offs made when moving to QLC.
I can see that 3D QLC NAND could get to 1000 P/E cycles but that the 850 EVO has a higher endurance than the 840 Pro is just not accurate - the 850 EVO is rated at 2000 P/E and the 840 Pro at 3000 P/E.
850 EVO may have a higher TBW but that is not the same as endurance. Nor are they likely to have established TBW in the same way since the 840 Pro had a TBW of 72TB if it was used as an enterprise-class drive.
Endurance for planar TLC NAND varies quite a bit too, for example the Kingston UV400 is rated at 400-500 P/E while the Plextor M7V is rated at 2000 P/E, despite using the same NAND and controller! So it is not like 1000 P/E is set in stone for planar TLC NAND.
Finally the 960 EVO was found by Nordichardware to be rated at around 1200 P/E despite using 3D TLC NAND with a Charge Trap.
@Glaring_Mistake Never saw an official endurance rating for the 850 EVO, so I was extrapolating from the TBW (note I didn't say P/E cycles here where it did later). The 840 Pro is a consumer drive, so I had no reason to believe they would be rated differently. I did however come across this article when looking up your 2000 P/E number suggesting that the 850 EVO does in fact have less endurance than the 840PRO. Good catch there.
@Glaring_Mistake: "Endurance for planar TLC NAND varies quite a bit too, for example the Kingston UV400 is rated at 400-500 P/E while the Plextor M7V is rated at 2000 P/E, despite using the same NAND and controller! So it is not like 1000 P/E is set in stone for planar TLC NAND."
Perhaps, I should have specified that I was talking about Samsung planer TLC for that 1000 P/E cycles. I thought it was self evident as my comparison was between Samsung flash, but in hindsight, I did mention other companies as examples of who uses charge trap and floating gate.
I agree that TLC NAND varies, which is why I stuck with the same manufacturer and as close to the same controller as possible. Design of the cells, size of the cells, process, and even software considerations like error correction method can all contribute to the endurance of the NAND. This is why it is impractical to compare endurance of flash from different manufacturers using different controllers and running different firmware. The Kingston UV400 and Plextor M7V is a perfect example of how NAND with the same NAND and controller with identical physical endurance can get wildly different ratings depending on the firmware (different error correction methods). This does little to alleviate my fears regarding QLC and even gives me pause regarding TLC.
@Glaring_Mistake: "Finally the 960 EVO was found by Nordichardware to be rated at around 1200 P/E despite using 3D TLC NAND with a Charge Trap."
I'm guessing this is another unofficial rating, but it seems logical. I would expect the 960 EVO with Charge Trap base 3D TLC NAND NAND built on a smaller process to have less endurance than 850 EVO with Charge Trap base 3D TLC NAND built on a larger process. That's before your consider that you have a couple of generations difference in controller and firmware that makes it even harder to compare. I short, I'm not sure what you are trying to say here.
Unfortunately, despite all the data that suggests TLC has plenty of endurance for consumers, I can't bring myself to put a TLC drive in my personal system. I have not problem putting one in a client system after making sure they are fully aware of the trade-offs, though. However, I can't in good conscience recommend a QLC drive even with the 1000 P/E cycle rating as I know how they are getting there.
It's like comparing a higher quality recording to a recording with pops, artifacts, and distortion. In this case, they would call them equal because the listener on the junk recording was more adept and was able to understand the same number of words as the listener on the higher quality recording.
Just because you have better error correction, doesn't mean you haven't exceeded to limits of the NAND and caused errors. The more errors you have to contend with, the more you are playing a probability game of can you correct the errors and still retrieve your data, or will you hit a particularly bad sequence of errors that is outside of your error correction algorithm's ability to correct.
What firm do you do engineering work for again? May I see your whitepapers? With the move to 3D NAND I have no issues with good TLC drive. QLC... fine for storage, at the very least. At 1000 P/E it will likely have a lower average failure rate than HDDs, even for primary storage - not that I would use it for primary storage.
@Alexvrb What part of "Unfortunately, despite all the data that suggests TLC has plenty of endurance for consumers, I can't bring myself to put a TLC drive in my personal system." suggests that this is anything more than an opinion.
@Alexvrb: "What firm do you do engineering work for again? May I see your whitepapers?"
What exactly do you want me to prove here. I've already stated that there is plenty of data that suggests TLC had plenty of endurance for consumers. I didn't mention enterprise, but if you are talking enterprise, there are some use cases that require eMLC. If regular MLC isn't up to the task, then clearly TLC won't be for that scenario. If you are talking about the error correction method, there are plenty word dedicated to that in the article above. From Article "Also, to deal with read errors from QLC memory, controllers with very advanced ECC capabilities have to be used for QLC-based SSDs. Toshiba has its own QSBC (Quadruple Swing-By Codes) error correction technique, which it claims to be superior to LDPC (low-density parity-check) that is widely used today for TLC-powered drives."
Are you suggesting that I need to show you white paper before I can have an opinion of what performance and endurance I am willing to pay for? I tell my customers that there is minimal risk with a good TLC drive and a little more so with cheaper drives like the Kingston UV400, but controller failure often happens before the NAND wears out anyways. Furthermore, for most people, even the cheapest TLC drive last much longer than spinning media. If a client wants a QLC drive, I'll give it to them. I will not, however, suggest it to the client as at this point there are too many unknowns. A NAND endurance of 1000 P/E cycles is more than some TLC drives (Kingston UV400 gets half that). That said, it has not been tested and it is unknown whether they can actually pull it off. Also consider, that the number relies on advanced ECC capabilities. The effect this has on the controller is an unknown quantity. There were drives in TechReport's SSD Endurance test that failed without a single bad sector, suggesting the controllers were responsible: http://techreport.com/review/27909/the-ssd-enduran...
Full Disclosure: I have designed ASICs fabricated for and in use at Washington University's Radio Chemistry department (nuclear physics), so while I have no experience design pure memory chips, I do know a few things about silicon charge decay rates. Do you have any credentials to provide or did you think you could give yourself credibility by discrediting me?
Consumer SSDs are regularly being endurance tested, and invariably are proven to handle more wear than even a power user would put on a drive before it's hopelessly obsolete. There is no "trade-off" for someone buying a TLC drive unless they're sticking it in a datacenter.
The odds of the drive being lost to fire, theft, or alien abduction are much greater than some some crazy random chain of cell failures overpowering normal error correction.
A responsible advisor would simply tell his clients to regularly back up their data on PROPER archive media, and use the money they saved on some beers so they can relax.
@grant3: "Consumer SSDs are regularly being endurance tested, and invariably are proven to handle more wear than even a power user would put on a drive before it's hopelessly obsolete."
Agreed. Quick question: Do you have a line on endurance tests with anything newer than a Samsung 840 EVO? My 60 second GoogleFu has failed me in this regard. Of particular interest to me is offline data retention, which happens to be the number 1 storage failure issue I personally encounter with SSDs.
@grant3: "The odds of the drive being lost to fire, theft, or alien abduction are much greater than some some crazy random chain of cell failures overpowering normal error correction."
While the odds are great, I submit for you a counter example: http://techreport.com/review/27909/the-ssd-enduran... "The 840 Series didn't encounter actual problems until 300TB, when it failed a hash check during the setup for an unpowered data retention test. The drive went on to pass that test and continue writing, but it recorded a rash of uncorrectable errors around the same time. Uncorrectable errors can compromise data integrity and system stability, so we recommend taking drives out of service the moment they appear."
The workload is not a client workload, so this really isn't something to worry about. However, it proves that it can happen. By virtue of requiring stronger error correction, it stands to reason that QLC based drives are more likely to see this type of unrecoverable error than TLC drives. The process size the NAND is built on has also shrunk since then. Shrink the process a few more times and the odds may not be as far fetched as they once were.
@grant3: "A responsible advisor would simply tell his clients to regularly back up their data on PROPER archive media, and use the money they saved on some beers so they can relax."
Almost exactly what I tell them word for word. Almost never happens outside of businesses. They tell me up front they won't do it. I'll still put a TLC drive in as they usually last longer than spinning disk. However, given this situation QLC doesn't inspire as much confidence as I'd like (this is an opinion). One client I had with a proper backup solution in place still lost critical data because he relaxed the period between backups due to perceived performance issues on the network that were completely unrelated.
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ddriver - Monday, July 3, 2017 - link
QML for cold storage? What's that? Like a month and your data is gone? Woot!ddriver - Monday, July 3, 2017 - link
QLC that is...Drumsticks - Monday, July 3, 2017 - link
Is QLC actually any more vulnerable to letting electrons escape than any other cell type? I'm not exactly a NAND architect, but how would reading/writing based on multiple levels of voltage have an effect on the ability to keep a charge?If you wear out the cell, that's probably fair (and that happens faster in QLC for sure), but we're talking about WORM, so presumably that's less of an issue.
Probably worth bringing this up too if we're talking about data retention.
http://www.anandtech.com/show/9248/the-truth-about...
qap - Monday, July 3, 2017 - link
It doesn't have an effect on ability to keep charge. But if you double the number of charge levels and you are loosing charge at the same rate, you will get to the charge representing different level in half the time needed before.saratoga4 - Monday, July 3, 2017 - link
Not more vulnerable, but you have a lot fewer to lose before you flip bits.Leakage can be made very low though, especially on drives with adequate cooling.
HomeworldFound - Monday, July 3, 2017 - link
So say I archived my files on a bunch of SSDs. Would I need to plug them into a power station or something every so often just to keep my archives intact? If so how often and long would that need to occur on your average SSD?EnzoLT - Monday, July 3, 2017 - link
Considering my Pokemon Blue cartridge still has my save game files today, I'd say a pretty damn long time..jimjamjamie - Tuesday, July 4, 2017 - link
Ah yes I forgot Toshiba initially used 3D QLC NAND in game boy cartridgesGuspaz - Tuesday, July 4, 2017 - link
Pokemon Blue stored the save game in volatile memory (SRAM) and used a battery to keep it powered. Your save is still there because the sram has an extremely low power draw.Lolimaster - Wednesday, July 5, 2017 - link
Those use ROM+eeprom not nand-flash, a totally different type of storage.Freakie - Monday, July 3, 2017 - link
Read hot, store cold is the rule for SSDs. The hotter the environment they are in while they are active, the less wear and tear on the cells because it's easier to move the electrons around. The colder you store them, the harder it is for electrons to leak.Freakie - Monday, July 3, 2017 - link
I guess that should be "Use hot, store cold" not read hot. But you get the point.beginner99 - Wednesday, July 5, 2017 - link
Why would you use an SSD to archive and not a cheapo hdd at a fraction of the cost and with less issue of losing data?HomeworldFound - Wednesday, July 5, 2017 - link
I generally wanted know how much of a bad idea that was, ignoring the cost, and how far away the industry is from having non-mechanical drives for storage purposes where some of us don't like mechanical drives very much.HomeworldFound - Wednesday, July 5, 2017 - link
Oh, and one thing I meant to mention were the transfer speeds and noise etc. After all of these years I'm very tired of the time spent, the noise and vibration.azazel1024 - Thursday, July 6, 2017 - link
The answer is, yes. The spec for P/E cycles is 1yr of storage persistence once that is reached. So if it is a 5k P/E drive, at 5k P/E cycles, the storage should persist for a year, before it wouldn't be retrievable. Of course that is only a very good chance of the data being recoverable without errors, not a perfect guarantee.The lower the number of P/E cycles on the drive, the longer the data can be retrained error free. It isn't a log function and now I am too lazy to go pull up the white paper I had been reading on it for another Anandtech article I commented on recently. But an MLC drive they were looking at had something like 1/30-1/10th the raw read error rate of P/E count of 1 vs P/E count of 5,000 (I assume based on 2x nm flash drive, that was roughly the max rated P/E count for MLC).
So figure 10-20 years of data retention.
IF KEPT AT ROOM TEMPERATURE. NAND flash very rapidly loses charge at higher temperatures. At 70C, about what you could expect in a hot car on a sunny day with a black SSD enclosure with the sun right on it, it loses charge something like 300x faster. Even at 50C it accelerates data loss by something around 30-40x and 40C it is about 10-15x. This is all versus 20C storage.
So if you live in the tropics and leave SSDs laying around on a shelf in an unconditioned building, probably figure on a barely used drive you might get 1-2 years of data retention. On an abused drive, weeks. In the arctic you might get centuries of data retention.
MamiyaOtaru - Tuesday, July 4, 2017 - link
won't leak faster, but it's a lot easier to tell the difference between 0 and 1 (SLC) than it is to tell the difference between 0110 and 0111 (QLC). That is to say you can leak a lot before 1 looks like 0, but don't have to leak nearly as much before 0111 looks like 0110Pork@III - Tuesday, July 4, 2017 - link
Planned obsolescence...."QLC that is..."
....garbage!
Bullwinkle J Moose - Tuesday, July 4, 2017 - link
Planned obsolescence ???..."TOSHIBA that is!..."
Endurance claims appear higher than normal and consumer availability is conveniently after the Company will be sold to the highest bidder
Anyone sampling these now should torture the crap out of them to see if the endurance claims are anywhere near accurate before this Company Vaporizes as fast as its claims
Alexvrb - Tuesday, July 4, 2017 - link
I'm all for QLC... for secondary storage only. Basically replacing a storage HDD used for media with a QLC SSD. Current TLC drives are far too expensive to replace multi-TB HDDs. Anyway, in that scenario QLC would be good enough, you're not going to be hammering the drive with writes.For primary storage, a really good TLC based drive is a bare minimum. QLC, even supposed high endurance QLC, isn't good enough. Even if the endurance is truly as good as they claim, performance won't be. Especially when discussing PCIe-linked NVMe solutions (mostly M.2).
I envision a rig with an PCIe 4.0/5.0 main drive (possibly PCM/ReRAM), and a high-density QLC drive for mass storage.
mkozakewich - Wednesday, July 5, 2017 - link
Keep in mind, four bits is only 33% more than three bits. They immediately jumped to the idea of 100TB drives, but it looks like their upcoming QLC chips would support about 4TB. (Or 8 TB, maybe.)Alexvrb - Wednesday, July 5, 2017 - link
I have a 3TB HDD for secondary storage. A 4TB would be plenty. :D Pricing, of course, is key. I don't anticipate being able to go all-solid-state for at least a couple of years.Lolimaster - Wednesday, July 5, 2017 - link
For media you don't SSD at all, HDD's are plenty fast and responsive for it. Another thing is having a huge collection of images where you want to use the thumbnails often.beginner99 - Wednesday, July 5, 2017 - link
And the race to bottom just reached a new low. Won't be far till be reach JMicron level of bad.nandnandnand - Wednesday, July 5, 2017 - link
This article has some serious grammar problems. Maybe 4 mistakes in the first two paragraphs.Gasaraki88 - Wednesday, July 5, 2017 - link
I'm not trusting QLC with my data. Some TLC are bad enough. Maybe for WORM storage but no way for daily use. They can lie about the 1000 P/E cycles all they want.BurntMyBacon - Wednesday, July 5, 2017 - link
3D-QLC getting 1000 P/E cycles is not as improbable as it seems. Samsung's move to 3D-NAND brought an odd situation where the MLC based 840PRO had less endurance than the TLC based 850EVO. Intel / Micron didn't get this benefit as they chose to use floating gates instead of charge traps in their architecture. Samsung, SK Hynix, and Toshiba all use charge trap. If I recall correctly, the 1000 P/E cycles metric is where planer NAND ended up. It is conceivable that Toshiba was able to make a 3D-QLC NAND with equal endurance to its planer TLC predecessor similar to how Samsung achieved a 3D-TLC with greater endurance than its planer MLC predecessor.However, I don't recall ever hearing 1000 P/E cycles used to describe the endurance of a 3D-TLC (charge-trap) NAND chip. An appropriate comparison point would be Toshiba's 3D-TLC vs Toshiba's 3D-QLC. That would help us to understand the true trade-offs made when moving to QLC.
Glaring_Mistake - Wednesday, July 5, 2017 - link
I can see that 3D QLC NAND could get to 1000 P/E cycles but that the 850 EVO has a higher endurance than the 840 Pro is just not accurate - the 850 EVO is rated at 2000 P/E and the 840 Pro at 3000 P/E.850 EVO may have a higher TBW but that is not the same as endurance.
Nor are they likely to have established TBW in the same way since the 840 Pro had a TBW of 72TB if it was used as an enterprise-class drive.
Endurance for planar TLC NAND varies quite a bit too, for example the Kingston UV400 is rated at 400-500 P/E while the Plextor M7V is rated at 2000 P/E, despite using the same NAND and controller!
So it is not like 1000 P/E is set in stone for planar TLC NAND.
Finally the 960 EVO was found by Nordichardware to be rated at around 1200 P/E despite using 3D TLC NAND with a Charge Trap.
BurntMyBacon - Monday, July 17, 2017 - link
@Glaring_MistakeNever saw an official endurance rating for the 850 EVO, so I was extrapolating from the TBW (note I didn't say P/E cycles here where it did later). The 840 Pro is a consumer drive, so I had no reason to believe they would be rated differently. I did however come across this article when looking up your 2000 P/E number suggesting that the 850 EVO does in fact have less endurance than the 840PRO. Good catch there.
@Glaring_Mistake: "Endurance for planar TLC NAND varies quite a bit too, for example the Kingston UV400 is rated at 400-500 P/E while the Plextor M7V is rated at 2000 P/E, despite using the same NAND and controller! So it is not like 1000 P/E is set in stone for planar TLC NAND."
Perhaps, I should have specified that I was talking about Samsung planer TLC for that 1000 P/E cycles. I thought it was self evident as my comparison was between Samsung flash, but in hindsight, I did mention other companies as examples of who uses charge trap and floating gate.
I agree that TLC NAND varies, which is why I stuck with the same manufacturer and as close to the same controller as possible. Design of the cells, size of the cells, process, and even software considerations like error correction method can all contribute to the endurance of the NAND. This is why it is impractical to compare endurance of flash from different manufacturers using different controllers and running different firmware. The Kingston UV400 and Plextor M7V is a perfect example of how NAND with the same NAND and controller with identical physical endurance can get wildly different ratings depending on the firmware (different error correction methods). This does little to alleviate my fears regarding QLC and even gives me pause regarding TLC.
@Glaring_Mistake: "Finally the 960 EVO was found by Nordichardware to be rated at around 1200 P/E despite using 3D TLC NAND with a Charge Trap."
I'm guessing this is another unofficial rating, but it seems logical. I would expect the 960 EVO with Charge Trap base 3D TLC NAND NAND built on a smaller process to have less endurance than 850 EVO with Charge Trap base 3D TLC NAND built on a larger process. That's before your consider that you have a couple of generations difference in controller and firmware that makes it even harder to compare. I short, I'm not sure what you are trying to say here.
BurntMyBacon - Wednesday, July 5, 2017 - link
Unfortunately, despite all the data that suggests TLC has plenty of endurance for consumers, I can't bring myself to put a TLC drive in my personal system. I have not problem putting one in a client system after making sure they are fully aware of the trade-offs, though. However, I can't in good conscience recommend a QLC drive even with the 1000 P/E cycle rating as I know how they are getting there.It's like comparing a higher quality recording to a recording with pops, artifacts, and distortion. In this case, they would call them equal because the listener on the junk recording was more adept and was able to understand the same number of words as the listener on the higher quality recording.
Just because you have better error correction, doesn't mean you haven't exceeded to limits of the NAND and caused errors. The more errors you have to contend with, the more you are playing a probability game of can you correct the errors and still retrieve your data, or will you hit a particularly bad sequence of errors that is outside of your error correction algorithm's ability to correct.
Alexvrb - Wednesday, July 5, 2017 - link
What firm do you do engineering work for again? May I see your whitepapers? With the move to 3D NAND I have no issues with good TLC drive. QLC... fine for storage, at the very least. At 1000 P/E it will likely have a lower average failure rate than HDDs, even for primary storage - not that I would use it for primary storage.BurntMyBacon - Monday, July 17, 2017 - link
@AlexvrbWhat part of "Unfortunately, despite all the data that suggests TLC has plenty of endurance for consumers, I can't bring myself to put a TLC drive in my personal system." suggests that this is anything more than an opinion.
@Alexvrb: "What firm do you do engineering work for again? May I see your whitepapers?"
What exactly do you want me to prove here. I've already stated that there is plenty of data that suggests TLC had plenty of endurance for consumers. I didn't mention enterprise, but if you are talking enterprise, there are some use cases that require eMLC. If regular MLC isn't up to the task, then clearly TLC won't be for that scenario. If you are talking about the error correction method, there are plenty word dedicated to that in the article above.
From Article
"Also, to deal with read errors from QLC memory, controllers with very advanced ECC capabilities have to be used for QLC-based SSDs. Toshiba has its own QSBC (Quadruple Swing-By Codes) error correction technique, which it claims to be superior to LDPC (low-density parity-check) that is widely used today for TLC-powered drives."
Are you suggesting that I need to show you white paper before I can have an opinion of what performance and endurance I am willing to pay for? I tell my customers that there is minimal risk with a good TLC drive and a little more so with cheaper drives like the Kingston UV400, but controller failure often happens before the NAND wears out anyways. Furthermore, for most people, even the cheapest TLC drive last much longer than spinning media. If a client wants a QLC drive, I'll give it to them. I will not, however, suggest it to the client as at this point there are too many unknowns. A NAND endurance of 1000 P/E cycles is more than some TLC drives (Kingston UV400 gets half that). That said, it has not been tested and it is unknown whether they can actually pull it off. Also consider, that the number relies on advanced ECC capabilities. The effect this has on the controller is an unknown quantity. There were drives in TechReport's SSD Endurance test that failed without a single bad sector, suggesting the controllers were responsible:
http://techreport.com/review/27909/the-ssd-enduran...
Full Disclosure: I have designed ASICs fabricated for and in use at Washington University's Radio Chemistry department (nuclear physics), so while I have no experience design pure memory chips, I do know a few things about silicon charge decay rates. Do you have any credentials to provide or did you think you could give yourself credibility by discrediting me?
grant3 - Friday, July 7, 2017 - link
Consumer SSDs are regularly being endurance tested, and invariably are proven to handle more wear than even a power user would put on a drive before it's hopelessly obsolete. There is no "trade-off" for someone buying a TLC drive unless they're sticking it in a datacenter.The odds of the drive being lost to fire, theft, or alien abduction are much greater than some some crazy random chain of cell failures overpowering normal error correction.
A responsible advisor would simply tell his clients to regularly back up their data on PROPER archive media, and use the money they saved on some beers so they can relax.
BurntMyBacon - Monday, July 17, 2017 - link
@grant3: "Consumer SSDs are regularly being endurance tested, and invariably are proven to handle more wear than even a power user would put on a drive before it's hopelessly obsolete."Agreed. Quick question: Do you have a line on endurance tests with anything newer than a Samsung 840 EVO? My 60 second GoogleFu has failed me in this regard. Of particular interest to me is offline data retention, which happens to be the number 1 storage failure issue I personally encounter with SSDs.
@grant3: "The odds of the drive being lost to fire, theft, or alien abduction are much greater than some some crazy random chain of cell failures overpowering normal error correction."
While the odds are great, I submit for you a counter example:
http://techreport.com/review/27909/the-ssd-enduran...
"The 840 Series didn't encounter actual problems until 300TB, when it failed a hash check during the setup for an unpowered data retention test. The drive went on to pass that test and continue writing, but it recorded a rash of uncorrectable errors around the same time. Uncorrectable errors can compromise data integrity and system stability, so we recommend taking drives out of service the moment they appear."
The workload is not a client workload, so this really isn't something to worry about. However, it proves that it can happen. By virtue of requiring stronger error correction, it stands to reason that QLC based drives are more likely to see this type of unrecoverable error than TLC drives. The process size the NAND is built on has also shrunk since then. Shrink the process a few more times and the odds may not be as far fetched as they once were.
@grant3: "A responsible advisor would simply tell his clients to regularly back up their data on PROPER archive media, and use the money they saved on some beers so they can relax."
Almost exactly what I tell them word for word. Almost never happens outside of businesses. They tell me up front they won't do it. I'll still put a TLC drive in as they usually last longer than spinning disk. However, given this situation QLC doesn't inspire as much confidence as I'd like (this is an opinion). One client I had with a proper backup solution in place still lost critical data because he relaxed the period between backups due to perceived performance issues on the network that were completely unrelated.
vaibhav24 - Wednesday, April 10, 2019 - link
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