Comment by Lex-2008

Your comment, along with other users, suggests that TLC is a positive attribute for consumers, however, the transition from SLC and MLC NAND to TLC and QLC 3D-NAND actually marked a decline in the longevity of SSDs.

Using a mode other than SLC with current SSDs is insane due to the difference with planar NAND features, as the current 3D-NAND consumes writes for everything.

3D-NAND, To read data consume writes [0],

    " Figure 1a plots the average SSD lifetime consumed by the read-only workloads across 200 days on three SSDs (the detailed parameters of these SSDs can be found from SSD-A/-B/-C in Table 1). As shown in the figure, the lifetime consumed by the read (disturbance) induced writes increases significantly as the SSD density increases. In addition, increasing the read throughput (from 17MBps to 56/68MBps) can greatly accelerate the lifetime consumption. Even more problematically, as the density increases, the SSD lifetime (plotted in Figure 1b) decreases. In addition, SSD-aware write-reduction-oriented system software is no longer sufficient for high-density 3D SSDs, to reduce lifetime consumption. This is because the SSDs entered an era where one can wear out an SSD by simply reading it."

3D-NAND, Data retention consume writes [1],

    " 3D NAND flash memory exhibits three new error sources that were not previously observed in planar NAND flash memory:

    (1) layer-to-layer process variation, 
    a new phenomenon specific to the 3D nature of the device, where the average error rate of each 3D-stacked layer in a chip is significantly different;

    (2) early retention loss, 
    a new phenomenon where the number of errors due to charge leakage increases quickly within several hours after programming; and

    (3) retention interference, 
    a new phenomenon where the rate at which charge leaks from a flash cell is dependent on the data value stored in the neighboring cell. "

[0] https://dl.acm.org/doi/10.1145/3445814.3446733

[1] https://ghose.cs.illinois.edu/papers/18sigmetrics_3dflash.pd...

A decent rule of thumb if that if a drive uses TLC, it will probably say so in the spec sheet.

If it's left ambiguous then it's either QLC, or a lottery where the "same" model may be TLC or QLC.

I bought up a lot of 960 and 970 Pro models when the 980 came out and it was TLC, to have MLC drives for logs and caches. Little did I know that TLC was just the beginning of the decline and QLC was right around the corner for even enterprise!

I don't understand this logic. Consider the two possibilities here.

The first is that only weird tech people are interested in doing this. Then they might as well allow it because it's a negligible proportion of the market but it makes those customers favor rather than dislike your brand, and makes them more likely to recommend your devices to others, which makes you some money.

The second is that it would be widely popular and large numbers of customers would want to do it, and thereby choose the drives that allow it. Then if Samsung does it and SanDisk doesn't, or vice versa, they take more of the other's customers. Allowing it is the thing makes them more money.

Meanwhile the thing that trashes most SSDs isn't wear, it's obsolescence. There are millions of ten year old QLC SSDs that are perfectly operational because they lived in a desktop and saw five drive writes over their entire existence. They're worthless not because they don't work, but because a drive which is newer and bigger and faster is $20. It costs the manufacturer nothing to let them be more reliable because they're going in the bin one way or the other.

The status quo seems like MBAs cargo culting some heuristic where a company makes money in proportion to how evil they are. Companies actually make money in proportion to how much money they can get customers to spend with them. Which often has something to do with how much customers like them.