Be careful what you ask for, you just might get it. That’s essentially how it’s shaken out with the new generation of QLC solid-state drives. QLC, of course, refers to the quad-level cells in the latest NAND flash memory, translating into four bits of data stored per cell, and thereby increasing storage density over existing TLC or triple-level cell NAND by a hefty and instant 33 percent.
What’s not to like? With the Crucial BX500 and Adata SU630, quite a lot. The downsides to QLC memory are the same in character as every other increase in NAND memory cell data density to date. The problem is scope. When the original single-level memory cell was usurped by MLC cells, which store two bits per cell, both performance and endurance suffered. That happened again when TLC upped the ante to three bits per cell.
Here we are again with QLC memory, and thus far, the downsides have been even more painful. To put some really rough numbers on all this in terms of endurance, SLC memory is good for about 100,000 program-erase cycles. By the time you get to QLC NAND, you’re looking at more like 1,000. As for performance, suffice to say that QLC involves 16 possible voltage levels per cell, and that in turn makes reading and writing data extremely laborious. This is the context for Samsung’s new 860 QVO drive.
The 860 QVO is essentially a QLCpowered update to Samsung’s existing 860 EVO 2.5-inch SATA drive. As you’d expect from a Q