[userbinator]

SLC requires very little in the way of firmware, since the endurance is so high and BER so low that simple ECC and wear leveling is sufficient. TLC offers only 3x the capacity, but theoretically lasts 1/8th as long, as SLC NAND manufactured on an otherwise identical process; and the former also requires much more complex (hence more bug-prone) ECC and wear leveling algorithms too, which affects speed and power consumption. QLC is 4x the capacity for 1/16th the endurance.

Industry marketing (and accompanying irrational pricing) has basically persuaded consumers to choose an inferior product.

[photonbucket]

Q: Am I able to run my TLC/QLC ssd in SLC mode? As that sounds sometimes useful

[wmf]

Physically this should be possible but I've never seen an SSD that allows it. I think very very few customers would use it, but I'm still a little surprised no vendor offers it.

[userbinator]

I suspect it's heavily firmware-dependent, but I do wonder if taking a TLC drive and partitioning it to 1/3 of its advertised capacity will keep all the blocks in SLC mode, since the firmware, if it's behaving reasonably, should try to use SLC as much as possible just for the speed benefit that brings, and only start converting blocks to MLC/TLC once all the blocks have already been used in SLC mode.

Speaking of firmware, there appears to have been an effort at making an open-source SSD, but it seems rather inactive: https://news.ycombinator.com/item?id=19629298

[wmf]

Coincidentally I did some research on this topic the other day and I couldn't find any SSD model with unlimited SLC cache. They all have fairly low limits like 10% of overall capacity.

[wmf]

You're never going to convince people to pay 2x-3x more than they have to.

[bigDinosaur]

Why not? There's certainly a group of consumers who will pay more for higher quality. I'm one of them. 2-3x current SSD costs for a better quality SSD would be completely fine with me. You're not paying more than you have to for the same product, you're purchasing a different product.

[wtallis]

Intel tried that with Optane with disastrous results (from a financial perspective). SLC doesn't require much separate R&D and manufacturing infrastructure beyond what already exists to serve the markets for TLC and QLC. But that lower barrier to entry still hasn't led to many attempts to serve this niche. Apparently the people with real sales volume data are convinced there's less of a market for expensive and small consumer SLC SSDs than there is for consumer 8TB TLC or QLC SSDs that cost as much as a decent laptop.

[userbinator]

Apparently the people with real sales volume data are convinced there's less of a market for expensive and small consumer SLC SSDs than there is for consumer 8TB TLC or QLC SSDs that cost as much as a decent laptop.

They realised it's easier to keep making a profit when drives keep "wearing out" (i.e. failing to be a data storage device) on a consistent and short(ening) schedule. Just like SLC, Optane was too good.

"small" is relative. 8TB of QLC is 2TB of SLC. They will both cost the same (if anything, the SLC might even be cheaper from a firmware/controller development perspective) yet the former might last a few years, and the latter several decades.

[wtallis]

A 2TB SLC drive is going to fill up before an 8TB QLC drive wears out, so I don't buy the planned obsolescence argument. And in reality, the kind of consumer who would spend $1k on an SSD is going to move on from it within two or three years anyways in favor of a newer drive with a faster interface.

[userbinator]

It will fill up, and more importantly, the data will stay intact. The endurance and retention of SLC is high enough that you can trust it for more than a few years.

And in reality, the kind of consumer who would spend $1k on an SSD is going to move on from it within two or three years anyways in favor of a newer drive with a faster interface.

...or expect that it will last much longer than a cheaper one.

[verall]

TLC holds 8 levels per cell

[rhn_mk1]

Which is 3 bits, so 3x as much data.

[userbinator]

This is correct. "TLC" is a misnomer. 2^3 is 8, and TLC stores 3 bits per NAND cell, or 8 voltage levels. I suppose when they came up with "MLC" for 2-bit cells (4 voltage levels), which is now also a misnomer as all multi-bit cells are technically MLC, they did not expect to put more than 2 bits in one cell.

[rhn_mk1]

The downvotes make me wonder how much useful discussion on HN is actually lost because of ignorants who prevent valid/factual information from surfacing.

[userbinator]

I wouldn't call them "ignorants". I'd say it's deliberate.