With QLC, SSD Manufacturers Target Hard Drive’s Final Strength: Raw Capacity


Just over two years ago, Micron became the first company to launch commercial products based on QLC (quad-level cell) technology. Intel followed with consumer-facing products later in 2018. These drives can hold up to four bits of data per cell, but they pay for the additional capacity with lower performance and lower longevity; QLC drives do not support nearly as many program/erase cycles as TLC drives, which are not as robust or as fast as MLC drives. The drop in SSD prices last year may have hampered QLC’s adoption — with all types of NAND storage cheap, QLC didn’t stand out as clearly — but manufacturers are still moving to adopt the technology. Recent leaks on Amazon indicate Samsung is planning to leap into the fray, with SSDs at 1TB and 8TB capacities, the latter priced at just $900.

For years, manufacturers have shown off improbably enormous SSDs with unstated (but equally enormous) price tags. Launching an 8TB SSD with a price tag of $900 works out to 11.2 cents per GB. The cheapest 1TB SSDs right now are below $100, meaning you’d pay around $750 to assemble the cheapest array of 1TB SSDs possible (not counting shipping), or potentially $900 to have all that capacity in a single drive. As capacity charges go, that’s a pretty small one — and it’s part of why we think the advent of QLC will allow SSD manufacturers to pressure HDD manufacturers in the one area where they’ve still held sway: Sheer capacity. An 8TB drive for $900 is a substantially better deal than 4TB for $1500, which is where we were back in 2016.

QLC-NAND

At the highest end of the market, HDDs will continue to have advantages; nobody is going to drop a reasonably-priced 16TB SSD in the near future, while a 16TB HDD will set you back just $386 according to Newegg.

Pushing QLC capacities higher will help the drives in two specific ways. First, it allows for larger SLC caches. Most QLC drives use an SLC cache to improve performance, with the size of the cache being determined by the base capacity of the drive. Intel’s 512GB 660p SSD has an SLC cache of between 6GB – 76GB depending on how full the drive is, while the 2TB version has an SLC cache of 24-280GB. Samsung will provision its own caching system differently than Intel, but larger drive capacities typically mean larger caches, which means less chance of hitting low performance, even with large file writes.

Second, it indirectly improves drive longevity by increasing the total amount of reserve NAND on the drive and spreading the writes out to a larger number of blocks. SSDs use a technique known as wear-leveling to reduce wear-and-tear on specific areas of the drive. The larger your drive is, the more capacity you have to perform wear-leveling in the first place.

In short, larger QLC drives won’t be free from the weaknesses of the medium, but end-users will be less likely to encounter those weaknesses in day-to-day usage. At the same time, QLC drives — while slower than other SSDs — are much faster than spinning discs, as this THG review of the 660p shows:

Image by Tom’s Hardware

These results reflect overall system responsiveness, underscoring the difference between an SSD and HDD. The Intel 660p is about 3 percent slower than an Optane drive, and 2.62x faster than a WD Blue. Obviously we’re leaning on Intel results to give us an idea of how a QLC Samsung drive may perform, but the basic concepts should all transfer — QLC drives are expected to use SLC caches and good drive management to minimize performance impacts, but QLC NAND is slower than TLC or MLC, and if you hit the drive with the right kind of test, those differences will appear.

With Intel now working on PLC (penta-level cell, or 5-bit) NAND, the push is on to shove magnetic disks out of the consumer market altogether, even with respect to capacity. The difference between the $154 price of an 8TB spinning disk and the $900 hypothetical price for an 8TB Samsung QLC drive is smaller, statistically, than the capacity and price differences between SSDs and HDDs that have already been overcome.

Samsung hasn’t even formally announced these drives yet, but thanks to now-defunct Amazon pages, we have the model numbers: MZ-77Q8T0B/AM (8TB) and MZ-77Q1T0B/AM (1TB). 2TB and 4TB models are considered likely. At $900 for 8TB, these drives won’t end the HDD market — but for consumers, at least, the writing is firmly on the wall. 7-8 years ago, the challenge for enthusiasts was buying an SSD that was large enough to be useful without breaking the bank, and many users still relied on HDDs for large-scale storage. We’ve long since passed the “large enough to be useful” stage, and are entering the era where consumer market SSDs are large enough to match the high-capacity drives a customer might consider, at prices close enough to make them think about whether tradeoffs are worth it.

I don’t think hard drives are going to die — enterprise sales remain strong on the whole — but I do think we’ll see fewer and fewer of them in consumer products as time goes by, even at the low-end. That’s not a bad thing.

While I harbor a sneaking admiration for the way HDD manufacturers have repeatedly driven higher capacities over the decade, the single best upgrade to breathe new life into an older PC is an SSD swap. The only thing that even comes close is a RAM upgrade, and only in scenarios where the machine has far less RAM for a given task than it ought to have. In that context, you’re arguably correcting a configuration flaw as opposed to strictly “upgrading” a PC.

Samsung hasn’t announced the hardware yet, so we can’t give you launch dates or full pricing, but we’ll keep an eye on these drives.

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