Understanding TLC NAND
by Kristian Vättö on February 23, 2012 1:14 PM EST- Posted in
- Storage
- SSDs
- OCZ
- Indilinx Everest
- TLC
Our thoughts are a bit mixed. On the one hand, cheaper SSDs are exactly what consumers want. The performance is still there compared to hard drives, no matter what NAND is used. If you go to an Apple Store today and try out MacBook Air and Mac Pro, the MacBook Air will often feel faster, even though it's the slower Mac in terms of processing power. This is solely due to the presence of an SSD. An SSD can bring new life to a computer that is otherwise considered obsolete. That's why we think everyone would want an SSD, but it's understandable that the masses won't adopt SSDs until the price and capacities are reasonable. This is definitely where TLC shines—it provides us with noticeably cheaper SSDs, possibly cheap enough for the masses to adopt (e.g. well under $1 per GB).
On the other hand, we're concerned that the cut in prices is done at the expense of endurance. One advantage often heard about buying an SSD is that SSDs are a lot more reliable than hard drives. In terms of P/E cycles, that is probably true with current MLC NAND. However, there have been quite a few widespread firmware issues, such as SF-2281 BSOD and Intel 320 Series 8MB bugs. Those have been fixed, and we may finally be looking at SSDs which have good performance, adequate endurance, and are more or less trouble-free. However, TLC will require new controller logic, and new logic may result in additional firmware issues.
The earliest SSDs lacked performance, even though they were faster than most hard drives, especially in seek times. In just a few years, performance has increased exponentially, maybe even to a point where the average user won't notice the difference between the fastest SSD and a mediocre SSD.
Given the desire for performance, reliability, and cost, TLC NAND may take away one from the triplet: endurance. Notice we said "may", because P/E cycles aren't everything. It has been claimed that algorithms to minimize write amplification will follow Moore's Law, just like NAND does. In other words, every time there is a die shrink, wear leveling has been improved in order to keep endurance the same. On top of that, improvements in manufacturing technologies can keep the P/E count up as well. 20nm IMFT MLC is claimed to have 3000-5000 P/E cycles, just like 25nm IMFT MLC.
The good news is, MLC NAND will stay in production and hence MLC NAND based SSDs are not going anywhere. What TLC will provide is freedom of choice. If you use your computer for checking email and browsing the Internet, no doubt a TLC based SSD will be sufficient. For the majority of consumers, TLC SSDs should meet their demands.
In addition, the SSD market is evolving quickly; if you buy the best SSD today, it won't be the best for very long. Let's say that it lasts you for four years. In that time, the SSD market will change a lot—four years ago, we were looking at 16GB SSDs for nearly $600! By the time a typical SSD is ready for replacement, you will be looking at much faster SSD with more capacity, and likely for a lower price. In 4.5 years, we have gone from that 16GB offering with performance that often trailed behind contemporary HDDs to 120GB SSDs that are up to a couple orders of magnitude faster than HDDs on random access patterns (and still several times faster for sequential tranfers), all for a starting price of around $170. If that pattern holds for the next four years, we'll be looking at ~1TB SSDs in four years that offer transfer rates that would saturate multi-lane PCIe interfaces at even lower prices. While we expect the rate of progress to be quite a bit slower over the next four years, there's still plenty of room for improvements in SSD technology.
As far as TLC-based SSDs are concerned, all we can do now is to wait for the first product announcements to come. Once we get some review samples, we'll be sure to put them through our SSD test suite and see how they stack up to existing drives.
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Beenthere - Thursday, February 23, 2012 - link
While the transition from SLC to MLC and now TLC sounds good, the reality is SSD makers have yet to resolved all reliability or compatibility issues with MLC consumer grade SSDs.Last time I checked OCZ was on firmware version (15) and people are still experiencing issues. The issues are with all SSD suppliers including Intel, Smasung, Corsair, etc. not just OCZ.
If data security is important it would be wise to heed Anand's advice to WAIT 6-12 months to see if the SSD makers resolve the BUGS.
extide - Thursday, February 23, 2012 - link
Go with an Intel, Samsung, or Crucial drive. They are reliable and fast.Beenthere - Thursday, February 23, 2012 - link
Actually no one has any lock on SSD reliability. Intel, Samsung and Crucial have ALL had issues that required firmware updates to fix BUGS. We don't know how many more BUGS exist in their or other brands of consumer grade SSDs.Not all HDD drives have issues. Yes some do especially the low quality high-capacity SATA drives. That however is not a good reason to buy a defective SSD.
SSD makers are just cashing in on gullible consumers. If people will pay top dollar for defective goods, that's what unscrupulous companies will ship. If consumers refuse to accept CRAP products, then the makers will fix the products or go broke.
ckryan - Thursday, February 23, 2012 - link
Yes, because everyone knows HDDs are infallible, never die, and are very fast...Oh wait, none of that is true.
MonkeyPaw - Thursday, February 23, 2012 - link
As someone who tried to use a Sandisk controlled SSD recently, it's not as obnoxiously simple as you make it sound. It's one thing to know a drive will fail, it's another to experience BSODs every 20 minutes.Making proper backups is the solution to drive failure, but a PC that crashes with regularity is utterly useless. I don't hate SSDs, I just want more assurance that they can be as stable as they are fast.
martyrant - Thursday, February 23, 2012 - link
So I've had the Intel 80GB X-25M G2s since launch with zero issues, no reason to upgrade firmware, no BSODs or issues. I recently bought one of their 310 80GB SSDs for an HTPC--again, 5 months later, no issues, no problems, no firmware updates.I've had a friend who's had two Vertex 2's in RAID 0 since launch with zero issues.
I also have a friend who has had a Vertex 2 drive die 4 times on him in under 2 months (this is more recent).
As of late, it seems that a lot of manufacturers are having issues but most I believe are the latest SandForce controllers which are causing the issues.
This is why you see people who use their own controllers, or one other than a recent SF controller, not having issues.
I feel bad, I really do, for those people who have been screwed over recently by the SSDs that have been failing--but I mean generally doing the research before hand benefits you down the road in the long run.
The reason Crucial, Intel, and Samsung SSDs are not having issues is because Crucial uses a Marvell controller, Intel uses its own controller, and Samsung uses it's own controller as well. This may not be true for all their drives, but most of their drives (the reliable ones) are of those controller types.
Just do your research before hand and don't be an SSD hater because they really are, when you shell out the cash to not get the cheapest thing on the market, the biggest upgrade you can do to your computer in the last 3-5 years. I haven't upgraded my mobo/cpu in either of my 3 computers in years but you bet I bought SSDs.
Holly - Saturday, February 25, 2012 - link
My OCZ Vertex 3 serves without glitch since 2.13 firmware was released. Before that occasional system freezing was major pain. Otoh I don't feel like updating to 2.15 firmware, rather being happy with what's working now :-)jwcalla - Thursday, February 23, 2012 - link
Yeah but even HDDs have major reliability problems... especially the high-capacity consumer drives.psuedonymous - Thursday, February 23, 2012 - link
There have been a few products already mixing an SSD with a HDD to allow oft-used data to be quickly read and written while rarely used bulk data that get's streamed (rather than random access) e.g. video is relegated to the HDD. Why not do the same with two grades of NAND? A few GB of SLC (or MLC) for OS files and frequently accessed and rewritten program files, and several hundred GB of TCL (or QLC, etc) for less frequently written data that it is still desirable to access quickly (e.g. game textures & FMVs). Faster than a HDD hybrid, cheaper than an all-SLC/MLC design, and just as fast in the vast majority of consumer use cases (exceptions including non-linear video editing, large-array data processing).kensiko - Thursday, February 23, 2012 - link
Yes that's what I thought reading this article.We just have to make the majority of writes on MLC and put the static data on TLC. Pretty simple and probably feasible in a 2.5in casing.